Hyperelastic binder for printed, stretchable electronics

ABSTRACT

Disclosed are compositions, devices, systems and fabrication methods for stretchable composite materials and stretchable electronics devices. In some aspects, an elastic composite material for a stretchable electronics device includes a first material having a particular electrical, mechanical or optical property; and a multi-block copolymer configured to form a hyperelastic binder that creates contact between the first material and the multi-block copolymer, in which the elastic composite material is structured to stretch at least 500% in at least one direction of the material and to exhibit the particular electrical, mechanical or optical property imparted from the first material. In some aspects, the stretchable electronics device includes a stretchable battery, biofuel cell, sensor, supercapacitor or other device able to be mounted to skin, clothing or other surface of a user or object.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent document claims the priority to and benefits of U.S.Provisional Patent Application No. 62/425,036 entitled “HYPERELASTICBINDER FOR PRINTED, STRETCHABLE ELECTRONICS” filed on Nov. 21, 2017. Theentire content of the aforementioned patent application is incorporatedby reference as part of the disclosure of this patent document.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under grant No.ECCS-1542148 awarded by the National Science Foundation (NSF) and grantNo. DE-AR0000535 awarded by Advanced Research Projects Agency-Energy(ARPA-E). The government has certain rights in the invention.

TECHNICAL FIELD

This patent document relates to systems, devices, and processes forflexible and stretchable electronics.

BACKGROUND

Conformal electronics are a new, emerging class of electronic devicesthat can conform to complex non-planar and deformable surfaces, such asliving tissue like skin, textiles, robotics and others. Conformalelectronic devices can include electric circuits and devices formed onflexible substrates that can be applied to and conform to a variety ofsurface geometries. For example, some flexible electronics have acapability that they can wrap or be bended, and can be shaped to fit tocurvilinear surfaces.

SUMMARY

Disclosed are compositions, devices, systems and fabrication methods forstretchable composite materials including triblock copolymer materials(e.g., thermoplastic elastomers) synthesized with a utility material toproduce elastic, functional materials, which can be used to formstretchable electronic components and devices.

In some aspects, a stretchable electronics device includes a stretchablesubstrate including an elastic and electrically insulative materialstructured to conform to an outer surface of an object; and an electrodearranged over the stretchable substrate, in which the electrode isformed from an elastic composite material including an electricalconductor, and a multi-block copolymer configured to form a hyperelasticbinder that creates contacts between particles of the electricalconductor within a network formed by the multi-block copolymer.

In some aspects, a stretchable battery includes a stretchable substrateincluding an elastic and electrically insulative material structured toconform to an outer surface of an object; a current conductor layerattached to the stretchable substrate, in which the current conductorlayer includes a first elastic composite material including a firstelectrical conductor and a multi-block copolymer configured to form afirst hyperelastic binder that creates contacts between particles of thefirst electrical conductor within a network formed by the multi-blockcopolymer; an anode attached to the current conductor layer and arrangedover the stretchable substrate, in which the anode includes a secondelastic composite material including a second electrical conductor andthe multi-block copolymer configured to form a second hyperelasticbinder that creates contacts between particles of the second electricalconductor within a network formed by the multi-block copolymer; and acathode arranged over the stretchable substrate, in which the cathodeincludes a third elastic composite material including a third electricalconductor and the multi-block copolymer configured to form a thirdhyperelastic binder that creates contacts between particles of the thirdelectrical conductor within a network formed by the multi-blockcopolymer, in which the stretchable battery is operable to store energywhile undergoing stretching.

In some aspects, a stretchable battery including a stretchable substrateincluding an elastic and electrically insulative material structured toconform to an outer surface of an object; a first electricalinterconnection structure and a second electrical interconnectionstructure each attached to the stretchable substrate and having aperiodic curved horseshoe geometry configured to connect unit cellregions positioned on the electrical interconnection structure, in whichthe first and the second interconnection structures include a firstelastic composite material including a first electrical conductor and amulti-block copolymer configured to form a first hyperelastic binderthat creates contacts between particles of the first electricalconductor within a network formed by the multi-block copolymer; aplurality of current conductor components attached to the electricalinterconnection structure at the unit cell regions, in which the currentconductor layer includes a second elastic composite material including asecond electrical conductor and a multi-block copolymer configured toform a second hyperelastic binder that creates contacts betweenparticles of the second electrical conductor within a network formed bythe multi-block copolymer; a plurality of anodes attached to the currentconductor component over the unit cell regions of the first electricalinterconnection structure, in which the anodes include a third elasticcomposite material including a third electrical conductor and themulti-block copolymer configured to form a third hyperelastic binderthat creates contacts between particles of the third electricalconductor within a network formed by the multi-block copolymer; and aplurality of cathodes attached to the current conductor component overthe unit cell regions of the second electrical interconnectionstructure, in which the cathodes include a fourth elastic compositematerial including a fourth electrical conductor and the multi-blockcopolymer configured to form a fourth hyperelastic binder that createscontacts between particles of the fourth electrical conductor within anetwork formed by the multi-block copolymer.

In some aspects, a method for producing a stretchable electronics deviceincludes providing an electrically conductive ink that includes anelastic composite material including an electrically conductive materialand a multi-block copolymer configured to form a hyperelastic binderthat creates contact between the electrically conductive material andthe multi-block copolymer; producing a first structure on a stretchablesubstrate by printing the electrically conductive ink through a firstportion of a stencil structured to have a first design to form thegeometry of the first structure, in which the stretchable substrateincludes an elastic material structured to conform to an outer surfaceof an object; and producing a second structure on the stretchablesubstrate to produce a stretchable electronics article by printing theelectrically conductive ink through the first portion of the stencil, ora second portion of the stencil structured to have a second design, orboth the first portion and the second portion, to form the geometry ofthe second structure, in which the stretchable electronics article isable to stretch at least 500% in at least one direction and to exhibitelectrical conductivity in the first structure while being stretched.

In some aspects, an elastic composite material includes a first materialhaving a particular electrical, mechanical or optical property; and amulti-block copolymer configured to form a hyperelastic binder thatcreates contact between the first material and the multi-blockcopolymer, in which the elastic composite material is structured tostretch at least 500% in at least one direction of the material and toexhibit the particular electrical, mechanical or optical propertyimparted from the first material.

Implementations of the disclosed technology can include one or more ofthe following features. In some example embodiments, the disclosedstretchable composite materials include an elastic, conductive inkhaving hyperelastic properties based on the formulation of triblockcopolymers, used as a hyperelastic binder, with conductive utilitymaterial(s), in which the hyperelastic binder is capable of toleratinghigh loadings of inelastic materials without sacrificing the elasticproperties of the stretchable composite.

In some example embodiments, a stretchable zinc-silver (I) oxiderechargeable battery in accordance with the present technology includespolystyrene-polyisoprene-polystyrene as a binder for elastic,electroactive inks. The example multi-component device can be producedby the synthesis of multiple elastic inks including compositemetal/metal oxide powders (e.g., carbon black, zinc, silver (I) oxide)for its respective functionality. The example stretchable rechargeablebattery can be used to self-power stretchable electronics throughvarious deformations such as 100% stretching, twisting, andindentations.

In some example embodiments, formulations of conductive inks forstretchable electronics, implementation of random composite inks anddeterministic patterning using inexpensive, high-throughput screenprinting of stretchable electronics for epidermal, textile, robotics,internet of things (JOT), and in-mold applications, among others. Insuch embodiments, the stretchable electronics include a hyperelasticstructure of “nanoislands” and/or “nanobridges” formed from highlyconductive, elastic inks including example triblock copolymers andutility materials. The example island-bridge designs provide a macrolevel of stretchability for such engineered components and devices,e.g., produced via printing the conductive, elastic inks.

These, and other, embodiments and techniques are described throughoutthis document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an illustration of an example elastic composite material100 in accordance with the present technology.

FIG. 1B shows an illustration of example constituents of a solution toproduce an elastic composite material.

FIG. 1C shows an illustrative diagram depicting the release and stretchstates of an example of the copolymer of the elastic composite material.

FIG. 1D shows a diagram of an example embodiment of a stretchableelectronics Zn—Ag₂O battery in accordance with the present technologyproduced using an example elastic, conductive composite ink on astretchable textile.

FIGS. 1E-1I show photographs of the example stretchable battery shown inFIG. 1D while undergoing various stretching, twisting and straining.

FIGS. 2A-2E show images and data plots of strain mapping evaluations ofexample rectangular carbon electrodes formed using the example compositeink.

FIG. 3 shows SEM images of the example stretchable Zn—Ag₂O batteryfeatures as printed, 100% stretched, and released after ten 100%stretching iterations.

FIGS. 4A-4D shows data plots depicting the electrochemical performanceof the example stretchable battery.

FIG. 5 shows an illustrative schematic of an example fabrication method500 to produce a stretchable electronics in accordance with the presenttechnology.

FIG. 6 shows example data using 3D optical profiling of the exampleprinted carbon ink on bare spandex textile and on thermoplastic urethaneon spandex textile.

FIGS. 7A and 7B shows images of an example, custom motorized linearstage apparatus from an unstretched position to a stretched position,respectively.

FIG. 8 shows digital image correlation images of example Zn and Ag₂Oelectrodes printed on top of the optimized carbon electrode before andafter stretching.

FIGS. 9A and 9B show data plots of conductivity versus strain, andstress versus strain, respectively, of example SP:SIS composites.

FIG. 10 shows a data plot of strain distribution of an example sample.

FIGS. 11A-11K shows example embodiments of a stretchable island-bridge(IB) electronics device platform and a fabrication method in accordancewith the present technology.

FIGS. 12A-12H show a diagram depicting the geometry of exampleserpentine bridges and images and data plots pertaining to evaluation ofuniaxial stretching of example embodiments of stretchable IB electronicsdevices.

FIGS. 13A-13I show images and data plots pertaining to evaluation ofexample island-bridge designs of example embodiments of stretchable IBelectronics devices.

FIG. 14A-14E show images, illustrations and data for example embodimentsof a printed stretchable island-bridge zinc-silver oxide battery.

FIG. 15 shows a diagram of an example stretchable wearable sensor inaccordance with the present technology.

FIG. 16 shows a diagram of an example stretchable battery in accordancewith the present technology.

DETAILED DESCRIPTION

Conformal electronics are a new, emerging class of electronic devicesthat can conform to complex non-planar and deformable surfaces, such asliving tissue like skin, textiles, robotics and others. Composites usedfor conformal electronics can be amenable to high-throughput, low-cost,additive printing technologies that include screen, inkjet, flexography,and 3D printing. However, the properties of the functional and elasticmaterials are mutually antagonistic to the other, thus achievingstart-of-the-art functional (bulk) properties and high elasticity hasbeen limited.

The advent of flexible/stretchable electronics has cultivated the nextgeneration of sensors, photovoltaics, paper-like displays,wearable/implantable electronics e-textiles, optics, and soft robotics.Unlike their brittle and rigid predecessors, soft flexible/stretchableelectronics have the potential to intimately integrate with curvilinearsurfaces while withstanding the complex deformations common of humanorgans, textiles, or robotics. Unfortunately, the progress ofstretchable systems, specific to their mobility and independence, iscurrently constrained by bulky and rigid powering sources. Batterieshold the most promise owing to their high power and energy densities,rechargeability, and low-cost.

Some examples of existing stretchable batteries have been fabricatedthrough different approaches, such as deterministic composite and randomcomposite architectural approaches. The deterministic approach relies onsubtractive methods to render otherwise rigid materials, with bulkproperties, into deterministic structures such as “island-bridge” or“cable-type” batteries. By engineering elasticity with high-performancerigid electrodes, these stretchable batteries can withstand some levelsof strain, but without intrinsically stretching them. As such,stretchable batteries produced via the deterministic approach are nottruly stretchable devices. The random composite approach embedspercolations of highly conductive fillers (e.g., >10⁷S m¹, silvernanowires and carbon nanomaterials) into an elastomeric matrix. Unlikedeterministic composite, these devices are intrinsically stretchable asfillers maintain electrical contact by sliding along each other duringstretching. However, while some of these intrinsically stretchablebatteries have been reported, none of the stretchable devices producedvia the random composite approach are completely elastic systems. Forexample, the cycle ability, current density, or areal capacity of theserandom composite produced batteries are compromised when a rigidcomponent undergoes large physical strain. Moreover, both deterministicand random composite-designed batteries are not economical because theyrely on extremely expensive and low-throughput fabrication methods, suchas lithographic, spray/dip coating, or “cut-and-paste” techniques.

Currently, printed, non-rechargeable batteries is an emerging marketsupporting many wearable and disposable electronics, e.g., with onestudy expecting the market value to reach $1.2 billion by 2017, CAGR 46%from 2012. Presently, individual components are fabricated using asingle, inexpensive printing step through either dispensing, screen,roll-to-roll, or inkjet printing of composite inks.

Unlike comparable coating technologies, such as spray or dip coating,screen printing can actively control the design that can potentiallycombine both deterministic and random composites. The higher viscosityrequirements of screen printing allows high loadings of conductivefillers towards superior elastic performance and higher batteryoperation. The rheology of the ink is controlled by the compositeformulation of electroactive fillers, a binder, and a specific solvent.The binder plays the role of holding the ink components together and indictating the flexible and stretchable nature of the inks. The synthesisof stretchable inks is highly challenging since the battery experiencessignificantly higher strain levels during stretching as compared to justbending. The printing technologies and random composite-based inks canbe used to fabricate cost-effective and intrinsically stretchablebatteries. The fundamental challenge of using random composite is thatthe electrochemical properties of the fillers and elastic matrix aremutually detrimental to the other. This approach becomes overwhelminglychallenging for printed, stretchable batteries with poorly conductive,electroactive fillers (e.g., ˜10⁵ S m⁻¹).

New innovations in highly elastic matrix would greatly benefit theadvancement of stretchable power source devices, e.g., in particular,specially formulated inks that are formulated to allow the printedbatteries to be stretched 100% multiple times.

Disclosed are compositions, devices, systems and fabrication methods forstretchable composite materials including triblock copolymer materials(e.g., thermoplastic elastomers) synthesized with a utility material toproduce elastic, functional materials, which can be used to formstretchable electronic components and devices. Example embodiments ofthe disclosed stretchable composite materials include an elastic,conductive ink having hyperelastic properties based on the formulationof triblock copolymers, used as a hyperelastic binder, with conductiveutility material(s), in which the hyperelastic binder is capable oftolerating high loadings of inelastic materials without sacrificing theelastic properties of the stretchable composite.

Various functionalities for the disclosed elastic, functionalcomposites, e.g., such as inks, can range from conductors, insulators,dielectrics, semiconductors and ceramics using both inorganic and/ororganic functional fillers. In some embodiments in accordance with thedisclosed technology, the use of these triblock copolymers with specificpercolate, functional fillers can yield fabrication of printedstretchable electronics devices and systems for various technologies,for example, including but not limited to conductive components,electrical circuits, photovoltaic devices, thermoelectric devices,piezoelectric devices, light-emitting devices, electrochemical sensors,supercapacitors, physical sensors, triboelectrics, actuators, batteries,and biofuel cells. Such printed stretchable technologies can be mountedto a textile or skin for stretchable applications that requirecomfortability and high performance under deformation, as well as beused for in-mold electronics.

In some example embodiments, a stretchable zinc-silver (I) oxiderechargeable battery in accordance with the present technology includespolystyrene-polyisoprene-polystyrene as a binder for elastic,electroactive inks. The example multi-component device can be producedby the synthesis of multiple elastic inks with composite metal/metaloxide powders (e.g., carbon black, zinc, silver (I) oxide) for itsrespective functionality. The example stretchable rechargeable batterycan be used to self-power stretchable electronics through variousdeformations such as 100% stretching, twisting, and indentations.

In some example embodiments, formulations of conductive inks forstretchable electronics, implementation of random composite inks anddeterministic patterning using inexpensive, high-throughput screenprinting of stretchable electronics for epidermal or textileapplications. In such embodiments, the stretchable electronics include ahyperelastic structure of “nanoislands” and/or “nanobridges” formed fromhighly conductive, elastic inks including example triblock copolymersand utility materials. The example island-bridge designs provide a macrolevel of stretchability for such engineered components and devices,e.g., produced via printing the conductive, elastic inks.

In some implementations, example embodiments of highly elastic,conductive inks are used in low-cost screen printing techniques tomanufacture example embodiments of an all-printed stretchable Zn—Ag₂Orechargeable battery in accordance with the present technology. Theexample inks possess attractive hyperelastic properties (e.g., ˜1300%elongation) of polystyrene-block-polyisoprene-block-polystyrene (SIS) toprovide an elastic binder for customizable, printable inks, which can beemployed to produce stretchable batteries. For example, due to uniqueblock polymeric structure of long polyisoprene chain and shortpolystyrene terminal ends, SIS has superior elasticity and simplerprocessing compared to common elastomers, such as Exoflex® that requiresan additional curing (vulcanization) step to form the 3D crosslinkednetwork to impart truly elastic behavior. In contrast, for example, SIScan be incorporated in higher loadings while maintaining the mechanicaland electrochemical properties of the battery, as demonstrated inexample implementations of the highly elastic, conductive inks describedherein. The example resulting rechargeable Zn—Ag₂O battery demonstratesa reversible capacity density (e.g., ˜2.5 mAh cm⁻²) even after multipleiterations of 100% stretching, and represents an intrinsicallystretchable battery with the highest reversible capacity and dischargecurrent density, manufacturable by inexpensive printing methodsdescribed herein. The example SIS-based printed battery can withstandother severe torsional strains relevant to the wearer's movement. Inexample implementations, the mechanical properties of the stretchablebattery were evaluated using digital image correlation (DIC) andscanning electron microscopy (SEM), and the attractive electrochemicalcycling, impedance and mechanical properties of the stretchable batteryare presented.

EXAMPLE EMBODIMENTS

In accordance with some embodiments of the present technology, anelastic composite material for stretchable electronics includes (i) acopolymer material, such as a block copolymer, and (ii) a utilitymaterial, such as an electrical conductor, insulator, or semiconductormaterial. In some embodiments, the elastic composite material includesone or more utility materials. In some embodiments, the elasticcomposite material further includes one or more additives.

In some embodiments, the copolymer material includes a triblockcopolymer (ABA), e.g., such aspolystyrene-block-polyisoprene-block-polystyrene (SIS),styrene-ethylene/butylene-sytrene (SEBS),styrene-ethylene/propylene-styrene (SEPS), and other triblock copolymerswith grafted chains on the midblock polymer. In such embodiments, thetriblock copolymer forms a phase separation of soft isoprene blocks thatare physically crosslinked by nanoclusters glassy styrene blocks. Themechanical behavior of SIS's highly elastic network is similar tonetwork structure of chemically crosslinked rubber through irreversiblevulcanization with the added benefit of being processable as aconductive ink. As such, the triblock copolymers include hyperelasticproperties that can tolerate higher loadings of inelastic, functionalmaterials to form new materials, like inks, without sacrificing elasticproperties of the formulated ink. For example, SIS was used to formulatean example ink with silver flake, and the resulting elastic conductordemonstrated an extremely high conductivity of 2281 S/cm at 0% andfractured at 400%. The higher loading of functional or utilitymaterial(s) with the example soft, hyperelastic triblock copolymermaterials can achieve devices with bulk-like structure and performancewhile being mechanically durable.

FIG. 1A shows an illustration of an example elastic composite material100 in accordance with the present technology. The elastic compositematerial 100 includes a copolymer 101 and one or more utility materials102 dispersed in the material 100. In some example embodiments of theelastic composite material 100, the copolymer 101 includes a triblockcopolymer, such as SIS. Also, in some example embodiments, the copolymer101 includes other examples of a thermoplastic elastomer includingstyrene-ethylene/butylene-styrene (SEBS) block copolymer,styrene-ethylene/propylene-styrene (SEPS), styrene-butadiene-styrene(SBS) block copolymer, or other triblock copolymer with grafted chainson the midblock polymer. In some examples, the copolymer 101 includesfluorine rubber. The utility material 102 and the copolymer material 101form a highly conductive network based on the contacts of the utilitymaterial 102 with the copolymer 101. In the example of SIS, SEBS or SEPSas the copolymer 101, the example copolymer provides superior elasticproperties to the elastic composite material 100 which allows one toreduce the amount of non-conductive polymer material and load moreconductive fillers that results in more functional utility of theelastic composite 100, in which the network still maintains a stableperformance. In some example embodiments, the elastic composite material100 includes two or more types of elastic copolymer materials 101 in thecomposite material.

In some example embodiments of the elastic composite material 100, theutility material 102 includes one or more types of materials, which areselected based on their electrical, optical and/or mechanical propertiesto provide a functionality to the elastic composite material 100. Insome examples, the utility material 102 includes a bulk ormicro-/nano-scale material based on functional properties, such as anelectrical conductor, insulator, oxide ceramic, non-oxide ceramics,electrochemical, triboelectric, actuators, or semiconductor, optical oropto-electrical material, MEMS materials, etc.

In some example embodiments, the elastic composite material 100 includesone or more additive materials. The additive materials can include othermetals, polymers, ceramics, composite materials, and/ormicro-/nano-materials, e.g., nanoparticles, nanowires, nanofibers,nanoflakes, graphene or carbon nanotubes (CNTs), or other material. Forexample, a 1-2% additive material can provide high aspect ratio fillersthat improve durability, printability, conductivity, and appearance(e.g., color or degree of transparency/opaqueness) of the elasticcomposite material 100. In some examples, the additive material caninclude mineral oil to improve the durability (e.g., 1-2%). In someexamples, the additive material can include ZnO and bismuth oxide toimprove battery performance for a stretchable electronic device, such asstabile, recharge cycling (e.g., 5-10% each). In some examples, theadditive material can include polyamide brushes can improve thedurability by imparting self-healing properties. In some examples, theadditive includes a solvent that can be used to improve the formulationof elastic composite material 100 as an ink. Such example solvents canbe included such that the Hansen solubility parameter is matched withthe copolymer constituent, e.g., copolymer material 101, such as in arange of 7.7 to 9.4.

For example, the additive material can include polyvinylidene fluoride(PVDF), e.g., which can provide added durability to the elasticcomposite material 100 without affecting the functional propertiesprovided by the utility material 102, such as electrical conductivity.For example, a 1:1 ratio of SIS and PVDF in a solvent mix of Toluene/NMPcan be used improve the durability of the ink to be printed. In someexample implementations, the elastic composite material 100 can includeSIS, a conductive material (e.g., Zn powder (80% Zn: 20% Carbon SP)),and additive PVDF (e.g., 5% PVDF in NMP). For example, 1 gram of aSIS-PVDF mixture (e.g., 0.1 g SIS, 0.15 g PVDF in 5 mL Toluene/NMP) ismixed with 1 gram of the Zn powder, in which the mix is repeated andprinted on a substrate (e.g., polyimide).

FIG. 1B shows an illustration of example constituents of a solution toproduce an elastic composite material 100. In this example, the exampleconstituents of the solution include the ‘smart’ polymer, and theutility and additive materials, e.g., nanoparticles, graphene and/orother composite, mixed in a solvent liquid. For example, the solutioncan be applied to a surface to produce the elastic composite material ona substrate using a variety of techniques, e.g., including spraying,screen-printing, inject printing, doctor blading, spin-coating, and 3Dprinting on any surface. For example, modification of solvent ratios canallow printing of subsequent layers. For example, the ratio (of thecopolymer material 101 (e.g., thermoplastic elastomer) and the utilitymaterial 102 can affect the functional performance and durability of theelastic composite material 100. For example, addition of a thermoplasticpolymer <3% with addition of another polymer (e.g., additive material)can improve the durability of the product.

FIG. 1C shows an illustrative diagram depicting the release and stretchstates of an example of the copolymer 101, e.g., SIS. As depicted in thediagram, the block-polystyrene portion of polymer chains forms aphysical crosslinking e.g., due to the affinity of styrene to eachother, and the block-polystyrene crosslinking center is interconnectedby long chains of the block-polyisoprene. The copolymer 101 forms ahyperelastic binder that creates contacts between particles of theutility material 102 (and/or any additive materials) within a polymericnetwork formed by the copolymer 101, contained within the overallelastic composite material 100. As such, the elastic composite material100 is able to stretch and release independent of other materials toaugment polymers of the material. For example, unlike some conventionalstretchable materials that use polymers, the elastic composite material100 does not require a cross-linker for cross-linking strands of apolymer in the elastic composite material.

In some embodiments in accordance with the present technology,stretchable electronics devices include the elastic composite materialsto form the components of the device, e.g., including conductivecomponents, insulating components, and/or semiconductor components. Insome examples, the elastic composite materials are used to produce aprintable stretchable battery in accordance with the present technology.Printed batteries have already been well established by powering radiofrequency identification devices (RFIDs), wearable devices, sensors forremote monitoring, and electronic displays. For example, printedbatteries have been used to power transdermal drug delivery. Thesedevices are primarily used to deliver arthritic or cosmetic drugs on tocurved surfaces of the skin that deform. At the moment, many of theseprinted batteries are only flexible, but not stretchable, and thereforecan diminish the performance and wearer's comfort in a wearable system.The present technology includes a highly stretchable rechargeablebattery that can be printed onto stretchable substrates and laterapplied to no curvilinear substrates such as skin, textiles, androbotics. For example, a printed device such as a battery can bescreen-printed on to a film with an adhesive backing, which can betransfer to any surface such as skin, textile, automotive, electronicscasing. In some instances, the transfer of textile can use heat totransfer the film onto a shirt. Such devices have great potential topower other wearable electronics without diminishing the conformabilityand performance of the entire, wearable system.

FIG. 1D shows a diagram of an example stretchable electronics device,i.e., a Zn—Ag₂O battery, produced using an example elastic, conductivecomposite ink on a stretchable textile. In some implementations, theexample stretchable Zn—Ag₂O battery can be fabricated using screenprinting techniques to form the elastic components of the Zn—Ag₂Obattery on a stretchable textile using the example composite ink havingthe SIS-hyperelastic binder. The diagram depicts an example redox chargeand discharge reaction exhibited by the battery.

For example, the attractive mechanical properties of the elastic,conductive composite ink lead to the intrinsically stretchable,rechargeable and printable Zn—Ag₂O battery that can withstand a varietyof severe mechanical strains. In the example shown in FIG. 1D, twostretchable batteries were printed in a “NANO” design directly on top ofthe thermoplastic polyurethane (TPU) head sealed onto a textile (e.g.,spandex). On the “NANO” current collector, the respective electrodeswere printed to form two batteries, i.e., the “NA” and “NO” designs,which are connected in series to power a load or device, e.g., a 3Vwearable-based LED in this example. In this example, an additional sealbetween “A” and the second “N” was applied, e.g., to avoid possibleshort circuit.

FIGS. 1E-1I show photographs of the example stretchable battery whilebeing 0% stretched (FIG. 1E), while being twisted (FIG. 1F), whileundergoing indentation strains (FIG. 1G), while being 100% stretched(FIG. 1H), and while being stretched biaxially (FIG. 1I). The scale barin the photographs of FIGS. 1E-1I is 2.25 cm.

As shown in the photographs of FIGS. 1E-1I, the example stretchable“NANO” battery maintained a constant LED brightness regardless of severetorsional strain (FIG. 1F), indentations (FIG. 1G), 100% uniaxialstretching (FIG. 1H), and biaxial stretching (FIG. 1I). The exampleprinted battery was shown to withstand high tensile stress withoutincurring any macrolevel cracking or debonding.

These example images demonstrate the attractive mechanical properties ofthe example composite ink having the SIS-hyperelastic binder that allowsthe example rechargeable ZnAg₂O battery to undergo severe mechanicalstrains without sacrificing device performance. The disclosed technologyhas particular commercial promise in the field of wearable electronics.For example, many wearable devices require the device to be anatomicallycompliant and maintain performance during deformations exerted by dailymovement of the human body. The use of the example composite stretchablefunctional materials to formulate printable, stretchable electronics canbe implemented for several types of technologies, such as batteries,sensors, actuators, wireless transmitters and/or receivers, and others.

In accordance with some embodiments of the present technology, a methodfor producing an elastic, conductive ink includes dispersing thecopolymer material (e.g., triblock copolymer, such as SIS) in a solvent,e.g., with a similar Hillenbrand solubility parameter, to form anintermediate product, such as a resin. For example, triblock copolymersare typically found as crumbs, flakes, or pellets that will dissolve inthe specific solvent to form a resin with a viscosity dependent on theamount of polymer to solvent. Once dissolved, the method includes mixingthe utility material, as well as additive materials for certainembodiments, into the intermediate product (e.g., resin) to produce theelastic composite material, such as an elastic conductive ink. Themixing process includes accounting for processing parameters to obtainthe final print viscosity of the composite material. In some exampleembodiments, the method includes producing a printable, stretchableelectronics device, such as a wearable stretchable battery, by mixingbattery composite powders (e.g., Carbon black, Zn, Ag₂O) as the utilitymaterials into resins of the SIS/toluene. Once thoroughly mixed, e.g.,using a Flacktek mixer, the inks can be printed on to a substrate byscreen printing to produce the stretchable electronics device.

Example implementations of embodiments of the compositions, devices,systems and methods in accordance with the present technology aredescribed. The example implementations included performance examinationsof example composite materials in example embodiments of stretchableelectronics devices, such as wearable batteries and sensors, describedbelow.

FIGS. 2A-2E show images and data plots of strain mapping evaluations ofexample rectangular carbon electrodes formed using the example compositeink. FIG. 2A shows the example rectangular carbon electrodes at 0%stretching for a 1:1 ratio (image A), 1:2 ratio (image C), and 1:3 ratio(image E) and at 100% stretching for a 1:1 ratio (image B), 1:2 ratio(image D), and 1:3 ratio (image F). FIG. 2B shows a data plot of strainversus X position across a fixed Y position for the example rectangularcarbon electrodes, plotted over the dotted line. FIG. 2C shows a dataplot of the respective resistance monitored during the 10 cycles of 100%stretching iterations. FIGS. 2D and 2E show the respective resistancesat release and stretching, respectively. The scale bar in FIG. 2A is 1.0cm.

In some implementations, a non-contact optical method called DIC can beutilized for strain mapping of the printed carbon electrodes ofdifferent SP:SIS ratios (e.g., 1:1, 1:2, and 1:3) upon their stretching.DIC can be employed as a high-resolution imaging tool to analyze thedeformations of macroscale objects in real-time to identify faults inmaterials or design. In these example implementations, the surface isprepared with a white coat and random black speckle, a grayscaleintensity pattern can be mapped for each pixel in the digital image ofthe sample. The incremental displacements of each speckle on the surfacecan be tracked using this grayscale intensity between images before andafter the deformation. Algorithms are used to patch pixels into groupscalled facets, where strain on the object's surface can be correlatedbased on the changing dimensions of the facet. The strain (ε_(x), ε_(y))is calculated by the amount of change in size of the facet (traced byDIC) divided by the original size of the facet. Lower strain valueindicates that pixel did not change much in that particular spot. If thepixel does not change much, this indicates that the facet or thelocation on the sample was hard to deform. Sudden increase in the strainindicates plastic deformations caused by the cracks.

FIG. 2A show images demonstrating a 2D strain mapping (ε_(x)) of therectangular carbon electrodes (1:1 ratio, 1:2 ratio, and 1:3 ratio) from0% stretching (panels A, C and E) to 100% stretching in the x-axis(panels B, D and F). As the electrodes are stretched, there aresignificant changes in the strain mapping. For all the electrodes, thestrain on the textile surface is generally higher than that of theelectrode surfaces, as shown by the data plot of FIG. 2B. While asignificant drop in the strain is observed at the interface betweentextile and the electrode, the 1:1 ratio electrode shows the largerdrop. Furthermore, the strain distribution on the electrode surface ishighly irregular for the 1:1 ratio electrode, and is correlated to thephysical cracks of the electrode. Such strain distributions are moreuniform for the higher SIS-content electrodes, suggesting thatelectrodes with higher SIS content are not physically cracked in theoptical scale.

In addition to the DIC analysis, change in resistance during thestretching cycles were monitored, shown in FIG. 2C. For example, atstretched state, the 1:1 ratio electrode has consistently high andunstable resistance due to the electrode cracking observed from the DIC(FIG. 2D). For the other two electrodes, with higher SIS content, theresistance values are stable and similar at the stretched state ataround 2.3 kΩ. However, when the electrodes are released from thestretching motion, the 1:2 ratio electrode consistently demonstrates thelowest resistance among the three electrodes with 0.65 kΩ (FIG. 2E). Inaddition to DIC analysis and resistance studies, stress and conductivityof the three composite ratios were simultaneously measured as they werestrained. As shown in Table 1 and in FIGS. 9A and 9B, these measurementscan compare the Young's modulus, conductivity at 0% strain, conductivityprior to break, and elongation at break. For example, the 1:2 ratioelectrode offers the optimum condition among the three composites, withthe most favorable tradeoff between relatively high conductivity and alow Young's modulus. This ratio was utilized to fabricate the examplecarbon current collector electrode for the stretchable Zn—Ag₂O battery.

TABLE 1 Mechanical Characterization of SP:SIS Composite Inks Young'sConductivity at Conductivity Elongation Composite Modulus 0% StrainPrior to Break at SP:SIS Ratios (Psi) (S/m) (S/m) Break (%) 1:1 — 60 79% 1:2 725 44 0.68 474% 1:3 145 18 0.21 598%

FIG. 3 shows SEM images of the example stretchable Zn—Ag₂O batteryfeatures, including the carbon current collector (panel A), the Znelectrode (panel B), and the Ag₂O electrode (panel C) as printed; thecarbon current collector (panel D), Zn electrode (panel E), and Ag₂Oelectrode (panel F) as 100% stretched; and the carbon current collector(panel G), Zn electrode (panel H), and Ag₂O electrode (panel I) asreleased after ten 100% stretching iterations. The scale bar of FIG. 3is 50 μm.

Although no cracks are observed in the DIC, the resistance stillincreases upon stretching. Since the DIC can highlight areas of crackingat the macroscale, SEM is utilized to observe physical deformations onthe micron scale. Morphology of the optimized carbon electrode, Znelectrode, and Ag₂O electrode were observed before, during, and afterstretching. For example, in these example implementations, while nocracks are observed at pristine state, upon stretching, micro crackswere observed. The cracks on these electrodes lead to increase theresistance and limit the electron conduction pathways. Per size of thecracks, carbon electrodes have the smallest cracks compared to those ofthe Zn and Ag₂O electrodes. For the Zn and Ag₂O electrodes, electricalcontacts may be disturbed by such large cracks. For example, the carbonelectrode can be kept on the bottom of the Zn and Ag₂O electrodes tomaintain the electrical connection. Although the carbon electrodedisplayed cracks as well, they were minute and uniformly distributed,which allow the electrical connections to be well preserved. Afterreleasing the electrodes following 10 cycles of 100% stretching, boththe carbon and Zn electrodes regained their crack-free morphology whileAg₂O displayed only a minor crack.

FIGS. 4A-4D shows data plots depicting the electrochemical performanceof the example stretchable battery. FIG. 4A shows a data plot of thefirst cycle voltage profile of the stretchable battery cycled with 2 mAhcm⁻². FIG. 4B shows a data plot of the discharge capacity duringprolonged cycle, cycled with 3 mAh cm⁻². Stretching battery was 100%stretched ten times before the electrochemical cycling. FIG. 4C shows adata plot of an electrochemical impedance spectroscopy (EIS) analysis ofthe pristine state of the example battery. FIG. 4D shows a data plot ofan EIS analysis of the example battery stretched to 100%.

As shown in FIG. 4A, the first cycle voltage profiles show highdischarge capacity. The pristine battery has 3.78 mAh cm⁻² andstretching battery has 3.94 mAh cm⁻² capacity. Upon stretching, thedischarge capacity has slightly increased which is attributable to theenlarged active surface area from the cracks formed during stretching.It is notable that, in these examples, the average voltage decreasesafter stretching. This decreased voltage may be due to the increasedpolarization and is more detrimental during the charge. The stretchingbattery has higher discharge capacity whereas the charge capacity issignificantly lower than the pristine. Due to the increasedpolarization, the second oxidation reaction, Ag₂O+20H⁻+2e⁻->2AgO+H₂O,from the cathode has not occurred, resulting in lower capacity than thepristine battery during the prolonged cycle, shown in FIG. 4B. However,for both example cases of batteries, the prolonged cycle dischargecapacities are stable up to 30 cycles. The first cycle dischargecapacity during the prolonged cycle, the pristine has higher capacityclose to 3 mAh cm⁻², e.g., as compared to that of the stretching batteryof about 2.5 mAh cm⁻².

An electrochemical impedance spectroscopy (EIS) was carried out toexamine the polarization during the mechanical perturbation. Theelectrochemical cycling performance of the stretching battery wasexamined after 10 times of 100% stretching. EIS for the pristine andstretched battery were obtained at pristine state and when the batterywas 100% stretched, e.g., in order to understand the difference inpolarization of the battery, as shown in FIGS. 4C and 4D. In the EIS,high, medium, and low frequency regions are identified with the lightand dark vertical dotted lines in the insets. All three regions havecharge transfer resistance and the constant phase elements. Thedepressed semicircle in the medium frequency region represents thecharge transfer resistance of the ions in the electrolyte or the chargeof the Zn anode and Ag₂O cathode. The diameter of the depressedsemicircle can be used to estimate the charge transfer resistance (R₂)on the electrodes. After being stretched, the R₂ increases from 115Ω to540Ω. Before the depressed semicircle, the charge transfer resistance isrepresentative of the uncompensated resistance or the carbon currentcollector electrode in the high frequency region. The light (left-most)dotted line is used to estimate the charge transfer resistance (R₁) ofthe current collector. After being stretched, the R₁ increases from 215Ωto 2400Ω. After the depressed semicircle, the charge transfer resistanceis related to the electrochemical reaction in the low frequency region.This highly resistive behavior is commonly observed in the EIS when thespectrum is obtained at the voltage in which electrochemical reactioncan occur.

The above example results have illustrated the attractive properties ofthe example SIS elastomer used as the binder for highly stretchablelow-cost screen-printed batteries. As a triblock copolymer (ABA), theexample SIS material forms a phase separation of soft isoprene blocksthat are physically crosslinked by nanoclusters glassy styrene blocks.This self-assembled elastic network gives SIS superior elasticproperties and a lack of a vulcanization step simplifies synthesis ofthe product. For example, vulcanization is process that crosslinks thepolymers, where entropy drives these materials to forcibly retract totheir original shape after an applied deformation is removed. Thisprocess is unnecessary in synthesis of the elastic composite materialsin accordance with the present technology, such as the elasticconductive inks. Also for example, the SIS demonstrated excellentadhesion to substrate, obviating the need for adding non-conductivesurfactants commonly used to prevent delamination. For example, thestrong adhesion demonstrated by the example synthesized elasticconductive inks can be attributed to the high tack quality ofpolyisoprene group of the SIS binder. Such ability for impartingstretchability has led to printable batteries that display highperformance following multiple severe mechanical strains.

DIC has been shown to be a useful technique to map the tensile strainfor the various example stretchable electronic devices composed ofdifferent materials and unique compositions. As shown in FIG. 2A, thestrain mapping is different between printed traces based on three SP:SISratios because of the printed electrodes display a different mechanicalbehavior that is dependent upon the ratios of inelastic or elasticduring the ink synthesis. The interfaces between the materials ofdifferent elasticities such as printed electrode and the PU substratecan also be mapped. At the interface, abrupt decrease in the strain isobserved for all electrodes. For example, this can be because at theinterfaces, the electrode is thickest. For example, when squeeze movesthe ink across the cavities of the stencil, most amount of ink isaccumulated at the edges. Upon curing, the electrode is thickest at theedges. Because the edges are thicker than the core or outside of theedges, it is harder to displace these regions. To compensate for the lowstrain on the interfaces, for example, the textiles and thin printsexhibit the higher strains.

For these example implementations using the example printed stretchablebattery, the stress and conductivity vs. strain measurements providedadditional material characterization of the SP:SIS composites. As shownin Table 1, the example 1:1 ratio composite—as an individual unboundfilm—demonstrated poor mechanical resilience but the highest initialconductivity. In comparison, resistance measurements on the example 1:1ratio composite printed on the stretchable Exoskin® substratedemonstrated improved durability, reflecting its behavior as astiff-island on a soft matrix. The example 1:2 ratio composite exhibitsa trade-off of durability and conductivity between the two extremecomposite ratios (e.g., 1:1 to 1:3). Such optimal composite behavior isattributed to the engineering of rigid, conductive fillers with elasticpolymer binder toward developing highly stretchable inks for specificapplication. The voltage profiles of the first cycle show that thevoltage plateau decreases after stretching, as shown in FIG. 4A. Forexample, the lower voltage plateau indicates that the polarizationincreased. However, the SEM images of these example implementationsreveal that cracks formed during stretching disappears upon the release,shown in FIG. 3. This discrepancy may be due to the presence ofelectrolyte. Although the physical cracks may disappear, the electrolytemay soak in between the cracks and hinder the electrical pathway.Furthermore, in these example implementations, the stretched electrodeshowed the highest areal capacity during the first cycle (FIG. 4A). Forexample, this may be because the electrolyte has soaked the cracks andhas significantly increased the active surface area. When the electrodeis stretched, new surface area is exposed and the electrolyte soaks thenew surface. The stretched electrodes have the wider active surfacearea.

In the example EIS results, both R₁ and R₂ increase upon stretching, asshown in FIGS. 4C and 4D. The degree of rise is significantly differentfrom each other. The R₁ escalates by a factor of 11.2 whereas the R₂grows by a factor of 4.70. The R₁ is contributed by stretching thecarbon current collector electrode and R₂ is mostly contributed by theanode and cathode. While both the resistance values increase withrespect to the stretching, the R₁ increases more significantly. Thissuggests that the deformations derive the impedance in electricconnections more so than the electrodes. If the mechanical strain on thecurrent collector layer can be alleviated, the electrochemicalperformance can be greatly enhanced. For example, one of the bucklingdevice configurations, a serpentine configuration or cable type ofconfiguration can be employed to alleviate the mechanical strain. Sincethese configurations can reduce the mechanical strain, theelectrochemical performance can be largely improved with intrinsicallystretchable electrodes.

These example implementations demonstrate a successful fabrication andoperation of a printable, highly stretchable rechargeable Zn—Ag₂Obattery based on an example embodiment of the elastic composite materialincluding a hyperelastic SIS as a binder. In the example implementationsof the stretchable rechargeable Zn—Ag₂O battery, all the components ofthe battery were printed using the example high-throughput andinexpensive screen printing method. For example, to obtain the maximumperformance of stretchable electronics, systematic and vigorousmechanical studies utilizing DIC and SEM were conducted. Therechargeable Zn—Ag battery was shown to have reversible capacity densityof ˜2.5 mAh cm⁻² at 3 mA cm⁻² discharge current density even after therepeated cycles of 100% stretching iterations. Such performancerepresents an intrinsically stretchable battery with the highestreversible capacity and discharge current density. The excellentresiliency against severe battery stretching can be attributed to thesuperior elasticity of the exmaple SIS binder of the composite material,e.g., associated with its long polyisoprene chains with well-spaced,physically cross-linking styrene domains. The first DIC was implementedfor localized strain analysis of stretchable electronics, and furtheroptimization of the printed deterministic structures, new materials, andexpansion of DIC in the printing design (like the implementation ofdeterministic structures or sandwich battery designs) have the potentialto enhance the electrochemical performance and the understanding of themechanical properties of SIS-based batteries. The example compositematerial has the potential to outperform any conventional printed,flexible electronics and is envisioned to pave the way to enhance otherforms of energy storage technologies, e.g., including Li-ion batteries,supercapacitors, and photovoltaics towards self-power stretchableelectronics. These example SIS-based composite for printed devices canallow several degrees of freedom relevant to a wearer's movement, andcan be conformably utilized in diverse real-life situations.

Example embodiments of fabrication methods to produce the exampleelastic composite inks and example stretchable printed Zn—Ag₂O batteryused in the example implementations are described.

Example chemicals and reagents used in the example implementationsinclude Super-P® Conductive Carbon Black (“SP”), toluene (Alfa Aesar),200 proof Koptec (Decon Labs, King of Prussia, Pa.), Zn powder (AlfaAesar), Ag₂O powder (Alfa Aesar), Bi₂O₃ (Alfa Aesar), and universal moldrelease (Smooth-On®). KOH, LiOH, polyacrylic acid, and SIS (14% styrene)were obtained from Sigma Aldrich.

The example elastic composite inks were prepared as follows. The elasticcarbon current collector ink was prepared by first dissolving 1.10 g ofSIS pellets in 5 mL of toluene with analog vortex mixer (VWR) for onehour. Toluene was chosen as the SIS solvent due to their similarHillenbrand solubility parameters. Then 0.6 g of SP (carbon black) ismixed into the SIS solution in a dual asymmetric centrifugal mixer,e.g., using a Flacktek Speedmixer™, DAC 150.1 KV-K, at 3000 rpm for 5mins. After cooling the ink, 4 g of yttria stabilized zirconia grindingbeads (e.g., 3 mm diameter, Inframat® Advanced Materials) and additional4 mL of toluene were added and underwent further mixing of 3000 rpm for30 mins to thoroughly mix and achieve optimum viscosity. The elastic Znink was prepared by first dissolving 0.6 g of SIS pellets in 2.8 mL of80% v/v toluene and 20% v/v ethanol with analog vortex mixer for onehour. Then, 3.4 g of composite Zn powder (30 wt % SP, 60 wt % Zn, and 10wt % Bi₂O₃) were mixed into the SIS solution in the dual asymmetriccentrifugal mixer at 3000 rpm for 5 mins. After cooling the ink in air,2 g of the yttria-stabilized zirconia grinding beads and additional 1.5mL of the toluene/ethanol solution were added and underwent furthermixing of 3000 rpm for 30 mins. The elastic Ag₂O ink was prepared byfirst dissolving 0.6 g of SIS pellets in 2.8 mL of 80% v/v toluene and20% v/v ethanol with analog vortex mixer for one hour. Then, 3.0 g ofcomposite Ag₂O powder (20 wt % SP and 80 wt % Ag₂O) were mixed into theSIS solution in the dual asymmetric centrifugal mixer at 3000 rpm for 5mins. After cooling the ink in air, 2 g of the yttria-stabilizedzirconia grinding beads and additional 1.5 mL of the toluene/ethanolsolution was added and underwent further mixing of 3000 rpm for 30 mins.

The example stretchable Zn—Ag₂O battery devices included the followingfabrication processes. The printing process employed a MPM-SPMsemi-automatic screen printer (e.g., Speedline Technologies, Franklin,Mass.). The bold “NANO” and rectangle patterns were designed in AutoCAD(e.g., Autodesk, San Rafael, Calif.) and patterned into a stainlesssteel through-hole 12 inch by 12 inch framed stencils with a thicknessof 100 μm (e.g., Metal Etch Services, San Macros, Calif.). Athermoplastic PU sheet (e.g., ST604, Bemis Worldwide, Shirley, Mass.)was thermally bonded to smoothen the surface royal-blue colored highperformance spandex (e.g., Spandex World, New York, N.Y.) using atypical drying iron (e.g., T-fal Ultraglide, Parsippany, N.J.). AKeyence VHX1000 optical profiler measured the surface roughness betweenthe ink printed directly on textile and TPU bonded textile.

FIG. 5 shows an illustrative schematic of an example fabrication method500 to produce a stretchable electronics in accordance with the presenttechnology. The method 500 includes a process 510 to screen print theexample SIS/carbon ink in a desired shape based using a stencil 503based on a desired stencil design over a substrate 505. In the exampleshown in FIG. 5, a bold “NANO” design is precut into a stainless steelstencil on the substrate 505, and the example substrate 505 includes athermoplastic PU sheet 505 a that is thermally-bonded to a flexible basesubstrate 505 b, e.g., spandex. For example, the printed SIS/carbon inkcan be used to form a current collector component of the stretchableelectronics device, e.g., stretchable Zn—Ag₂O battery. In someembodiments, the method 500 includes curing the screen printed ink,e.g., for each ink printing deposition or at least some of the inkprinting depositions. After curing the example SIS/carbon ink, themethod 500 includes a process 520 to print a stretchable anode 521(e.g., the stretchable SIS/Zn feature 521 shaped based on the top halfof the both letters “N” portions of the stencil 503), and/or a process530 to print a stretchable cathode 531 (e.g., the stretchable SIS/Ag₂Ofeature 531 shaped based on the letter of “A” and “O” portions of thestencil 503), e.g., by simply changing the stencil position, to producea printed stretchable electronics device, such as the example printedstretchable battery 535. In some embodiments, the method 500 includes aprocess 540 to connect the pairs of stretchable batteries by printing astretchable ink to form one or more other features 541 of thestretchable electronics device, e.g., such as connecting the letterpairs in series by a 3V textile based LED 551. In some embodiments, themethod 500 includes a process 550 to produce a protective sheet overcertain portions of the produced stretchable electronics device. Forexample, an electrolyte gel can be applied to each pair separately andheat sealed using a thin PU sheet to prevent leakage and mixing ofelectrolyte between the pairs. In some embodiments of the stretchableelectronics battery 535, the arrangement of the anode 521 and thecathode 531 can be built vertically, in which an electrolyte material isstructured between the anode and cathode.

In the example implementations, for example, carbon ink was used toprint the entire “NANO” design as the current collector onto a bondedtextile and cured in an oven at 80° C. for 15 mins. Subsequently, ananode electrode was printed with the Zn ink on the top half of bothletter ‘N’ carbon prints and cured in an oven at 80° C. for 15 mins.Lastly, a cathode electrode was printed with the Ag₂O ink on the tophalf of the letters ‘A’ and ‘0’ carbon prints and cured in an oven at80° C. for 15 mins. This example design produces two batteries that areconnected in series. The outline of the battery was heat-sealed with 26μm thick PU sheet (e.g., Delstar Technologies Inc. Middletown, Del.).The sealed battery was filled with the electrolyte. The example “NANO”battery design was connected to a textile-embedded 3 V yellow LED (e.g.,Lilypad, Sparkfun, Niwot, Colo.). A complete detailed schematic of thedevice fabrication is shown in FIG. 6.

In some examples of the stretchable battery, an example elasticcomposite material to produce a carbon current collector component ofthe battery can include SIS (e.g., copolymer 101) having a % wt in arange of 40%-75% (e.g., 64% wt), and carbon black having a % wt in arange of 25%-60% (e.g., 36% wt), in which toluene is used as a solvent(e.g., 7 mL). In some examples of the stretchable battery, anotherexample elastic composite material to produce the carbon currentcollector component of the battery can include SIS (e.g., copolymer 101)having a % wt in a range of 40%-80% (e.g., 75% wt), and agraphite-carbon black mix (graphite:SP, 1:0.3) having a % wt in a rangeof 20 T-60% (e.g., 25% wt), in which toluene is used as a solvent (e.g.,10 mL, e.g., 4 g of SIS in 10 mL toluene).

In some examples of the stretchable battery, an example elasticcomposite material to produce a zinc anode component of the battery caninclude SIS (e.g., copolymer 101), and zinc powder. An exampleformulation of the example Zn anode composite material includes using3.153 grams of SIS Resin (e.g., 2.4 g of SIS in 11.2 mL (2250Toluene/550 Ethanol, and 3.593 grams of Zn powder (e.g., 75% Zn, 10%ZnO, 10% Bi₂O₃, 5% SP). In such configurations of the Zn-based elasticcomposite material for the anode, for example, the SIS includes a % wtin a range of 10%-40%, and the zinc composite powder includes a % wt inthe range of 60%-90%. For example, the zinc composite powder includesZn, ZnO, Bi₂O₃, and SP with respective weight ranges of 60-80%, 0.1-15%,0.1-15%, and 0.1%-20% SP.

In some examples of the stretchable battery, an example elasticcomposite material to produce a silver oxide cathode component of thebattery can include SIS (e.g., copolymer 101), and Ag₂O powder. Anexample formulation of the example Ag₂O cathode composite materialincludes using 3.133 grams of SIS Resin ((2.4 g of SIS in 11.2 mL (2250Toluene/550 Ethanol), and 3.1593 grams of Ag₂O powder (e.g., 3003.5 gramof Silver Oxide, 150.2 grams of carbon black (e.g., Super-P)). In suchconfigurations of the Ag₂O-based elastic composite material for thecathode, for example, the SIS includes a % wt in a range of 5%-40% andAg₂O composite powder having a % wt in the range of 60%-95%. Forexample, the silver oxide composite powder includes Ag₂O and SP withrespective weight ranges of 60%-80% and 0.1%-20%, respectively.

For example, the addition of ethanol can be used for improving theprinting the anode/cathode components on to the current collectorcomponent. In some example experiments, it was found that a completetoluene solution in the cathode/anode sometimes led to cracks thecurrent collector when printed on top of it. The ethanol addition wasshown to reduce the reactive of the solvent, e.g., the Hansen solubilityparameter, that allows the ink to be printed on top of the ink withgreat adhesion and electrical connectivity.

FIG. 6 shows example data using Keyence VHX 3D optical profiling of theexample printed carbon ink on bare spandex textile (panel A) and onBemis Thermoplastic Urethane as smooth interface layer on spandextextile (panel B).

The DIC, SEM, and electrochemical tests were conducted using a pair of0.9 cm by 3 cm rectangle for the current collector layer and 0.7 cm by0.9 cm rectangle for the cathode and anode electrodes on a pre-appliedPU film commercially named as 9EX-2497P Exoskin® (Dartex Coatings Inc.,Slatersville, R.I.).

The example implementations included DIC tensile stress analysis. Inthese example analyses, carbon current collectors based on threedifferent SP:SIS ratios (1:1, 1:2, and 1:3) were printed on a dog boneshaped cutouts of Exoskin®. The carbon inks were using the same SISsolution as the earlier carbon ink. A while spray paint (e.g., FlatWhite Prime, Rust-oluem®, Vernon Hills, Ill.) then a random speckleblack pattern (e.g., Flat Black Prime, Rust-oluem®, Vernon Hills, Ill.)were lightly sprayed on the printed samples. The printed samples werestretched using a motorized test stand (e.g., Mark-10, Copiague, N.Y.)at a constant speed while a pair of high resolution, digital chargecoupled device (CDD) cameras was recording a video of the sample fromthe relaxed to stretched state of 100%. A commercial software GOM ARAMIS(e.g., Trillion Quality Systems, Plymouth Meeting, Pa.) was used toconvert the video into single frames for strain mapping. The blackspeckle on the white coating can create a grayscale matrix per pixel,which tracks the surface displacements of the deformed materials.Mathematical correlation functions are applied to grayscale distributionfrom the speckle patterns and are analyzed among images before and afterthe deformation.

The example implementations included mechanical and conductivitycharacterization of the example SIS composite inks. In these exampleanalyses, three current collector electrodes from the DIC experimentwere used to measure the resistance during and after the stretchingcycles. The sample preparation was same as the DIC experiment. Thestretching tests were conducted on a custom stretching stage of amotorized linear stage and controller (e.g., A-LST0250A-E01 StepperMotor and Controller, Zaber Technologies, Vancouver, Canada), which isdepicted in FIGS. 7A and 7B.

FIGS. 7A and 7B shows images of an example, custom motorized linearstage apparatus from an unstretched position to a stretched position,respectively. The samples were programmed to constantly stretch at aspeed of 0.1 cm second⁻¹ from 0% to 100% and back to 0% as one cycle.The resistance was measured at 22 pt sec⁻¹ using a digital multimeter(e.g., Agilent, Santa Clara, Calif.) during the ten cycles. The speedand length of the physical strain were programmed into a scriptingsoftware (e.g., Zaber console, Zaber Technologies, Vancouver, Canada).Additional mechanical characterization of the composites such as Young'smodulus, elongation at break, conductivity at 0% strain and conductivityprior to break were conducted. The same composite SP:SIS ratios (e.g.,1:1, 1:2, and 1:3) were prepared by printing on glass slides pre-coatedwith universal mold release. After curing the samples, the printedsamples were easily released from the glass slide and mounted to thecustom stretching stage. On one end of the stage, the mount wasconnected to a digital force gauge (e.g., Mark-10, Copiague, N.Y.) tomeasure the force applied while the sample is being strainedcontinuously by motorized linear stage. The resistance was measuredsimultaneously using a digital millimeter. Further calculations based onresistance and force measurements were completed to compare the stress(kN/m²) and conductivity (S/m) of the composite inks as they arestrained.

SEM images of the example electrodes included the following. The printedcarbon electrode, Zn electrode, and Ag₂O electrode were adhered onto aSEM holder. The pristine samples were adhere as printed without anystretching. The stretched samples were adhered with a 100% stretch. Therelaxed samples were adhered after the electrodes were repeatedlystretched 100% for 10 cycles. The images were taken using 10 kV energysource using FEI/Philips XL30 ESEM (Philips,).

The example implementations included characterization of theelectrochemical properties of the stretchable device. For example, allelectrochemical tests were conducted at room temperature. Theelectrochemical cycling tests were conducting with Arbin electrochemicalcycler channels, for example. Electrochemical cycling tests wereconducted with 2 mA cm⁻² first formation cycle and 3 mA cm⁻² dischargecurrent and 2 mA cm⁻² charge current for the subsequent cycles. Thedischarge cut-off voltage was 0.8 V and the charge cut-off voltage was2.3 V with 20 min constant voltage step. For bending and stretchingelectrodes, the batteries were electrochemically cycled after beingrelaxed for 30 mins. The EIS was conducted using a 10⁵-10⁻² Hz frequencyrange with 10 mV amplitude using Solartron 1287 electrochemicalinterface. All EIS tests were conducted at the open circuit voltage uponthe formation cycle.

Other example results using the example printed stretchable Zn—Ag₂Obattery included the following.

Table 2 shows an example comparison of cycle life, current density,areal capacity, and stretchability of an example embodiment of astretchable battery with other conventional flexible batteries.

TABLE 2 Cycle Life Before Stretching After Stretching (80% CurrentCapacity Current Capacity System retention) (mA cm⁻²) (mAh cm⁻²)Stretching (mA cm⁻²) (mAh cm⁻²) Conventional 8 2 1.5 11% 2 0.25 Zn—Agsystem 1 Conventional 1000 1 0.23 80% 1 0.18 Zn—Ag system 2 Conventional4 0.33 2.2 75% 0.33 1.7 Zn—MnO₂ system 1 Conventional 1 0.18 3.9 150% 0.18 3.9 Zn—MnO₂ system 2 Example 30 3 3 100%  3 2.5 Zn—Ag system

Table 3 shows an example comparison of properties including elasticmodulus, elongation, and viscosities of elastic binders for stretchableelectronics.

TABLE 3 100% 300% Resin Modulus¹ Modulus² Elongation³ Viscosity⁴ ElasticBinder (psi) (psi) (%) (cP) Fluorine Rubber 275 — 440 — (Dai-el G801)Polyurethene 300 800 660 — (Tecoflex SG-80A) Silicone 10 — 900 3000(Ecoflex ® 00-30) (mixed) SIS 0.1 130 1300 800-1200 (Kraton ® D1161,(25% w/w in 15% styrene) toluene at 25° C.) ¹100% modulus: tensilestress at 100% elongation (ASTM D412) ²300% modulus: tensile stress at300% elongation (ASTM D412) ³Elongation: tensile elongationcorresponding to the point of rupture ⁴Resin Viscosity: initialviscosity of binder, solvent, curing agent (if applicable) prior toadding conductive fillers. Optimal range for screen printing inks is5000-8000 cP.

FIG. 8 shows digital image correlation images of example Zn and Ag₂Oelectrodes printed on top of the optimized carbon electrode beforestretching (panel A), and after stretching 100% (panel B).

FIG. 9A shows a data plot of conductivity (S/m) versus strain (%) ofexample SP:SIS composites. FIG. 9B shows a data plot of stress (N/m²)versus strain (%) of the example SP:SIS composites.

FIG. 10 shows a data plot of strain distribution of the example sample,e.g., using the stage shown in FIGS. 7A and 7B, shown over the dottedlines of FIG. 10.

In some aspects, the disclosed systems include stretchable island-bridge(IB) electronics devices and methods of their manufacture. In someimplementations, for example, the stretchable IB electronics devicesinclude printable devices based solely on high-throughputscreen-printing technology. The stretchable IB electronics devicesinclude stress-enduring, composite inks formed in a “island-bridge”design, such that the devices can be applied to both skin-worn andtextile-based applications. These devices can employ thick-filmfabrication techniques to incorporate a wide-range of materials anddesigns, thereby enabling new directions for stretchable electronicsthat were not possible before. Example advantages and practicalutilities of the disclosed stretchable IB electronics devices andfabrication methods are described, including example implementations ofa wearable zinc battery as an example. For example, by enabling cheaperprocessing alternatives and a utilization of unlimited materials,stretchable electronics are envisioned to replace current state ofrigid, bulk electronics and continue the ubiquitous of electronics onskin, robotics, and clothing.

After a decade of smartphones and wearable products proliferating intoevery aspect of our daily lives, the drive for smaller, thinner, andmore conformal electronics has invoked a shift in the electronicsindustry. A new generation of electronics, such as sensors, e-textiles,soft robotics, wearable electronics, energy storage devices, andhemispherical eye cameras, are being engineered to fit and flex with thesurfaces they attach to or interface with so that they becomeindistinguishable from that object, such as skin, clothing, etc. Designsthat enable the electronics to conform and deform move with its attachedstructure are referred to as “stretchable electronics.” This new classof electronics relies on its ability to seamlessly mate with curvilinearsurfaces while maintaining stable performance, even under extreme strainis applied. This enables novel form factors that were not possible withconventional electronics.

The fabrication of stretchable electronics has generally relied onmodifying composites via the following approaches: deterministic designand intrinsic materials properties. The deterministic design approachturns geometrically patterned, traditionally rigid materials into devicewhere extremely thin, serpentine-/coil-shaped interconnections, known asthe “bridges” are integrated to accommodate strain betweennon-deformable parts, usually the functional components known as“islands” and binds them onto a soft, stretchable substrate. Thedeterministic design approach offers some advantage since the functionalcomponents do not intrinsically stretch, but can maintain consistentperformance when being stretched. Stretching can be achieved through inand out of plane buckling using selective bonding of islands to thesubstrate. Fabrication of this class of electronics devices typicallyuse subtractive, lithographic fabrication methods that are extremelyexpensive and low-throughput. Moreover, this class of devices arelimited to a small list of materials compatible with the fabricationtechniques, in addition to an expensive and complex, time-consumingfabrication steps.

Alternatively, the intrinsically stretchable class utilizes conductingpolymers where their molecular structures can be fine-tuned to enablestretchability. The properties of conductive polymers through solutionprocessing presents a more cost-effective approach than deterministicdesign approaches. Unfortunately, the use of conductive polymers arestill inferior electronic and semiconducting properties compared to bulkmetals and semiconductors.

Example embodiments and implementations of the disclosed stretchable IBelectronics devices, systems and methods are described. The exampleimplementations included performance examinations of example compositematerials in example embodiments of stretchable electronics devices,such as wearable batteries and sensors, described below.

FIGS. 11A-11K shows example embodiments of a stretchable island-bridge(IB) electronics device platform and a fabrication method in accordancewith the present technology. The example stretchable IB electronicsdevice platform includes deterministic structures suitable for epidermalor textile applications. For example, the all-printed IB structure areformed using printing techniques and creative integration of elasticcomposite inks and deterministic patterning. Example methods ofdepositing inks on to surfaces makes capable the printing of colorful,artistic designs for temporary tattoos, textiles, and electrochemicaldevices, such as for glucose monitoring, because of its affordability,high-throughput, and simplicity. In the examples described herein, thedesign of the conductive ink formulation includes ablock-polystyrene-block-polyisoprene-block-polystyrene (SIS) copolymer,which acts as a hyperelastic binder that provides the ink product withsuperior mechanical performance. In the produced elastic composite ink,the block-polystyrene part of polymer chains formed a physicalcrosslinking e.g., due to the affinity of styrene to each other, whileall the block-polystyrene crosslinking center were interconnected bylong chains from the block-polyisoprene. As such, a self-assembledhyperelastic nanostructure of “nanoislands” connected by “nanobridges”can be formed using the elastic composite ink. The fabrication methodemployed to produce the example stretchable IB electronics device cansolely utilize thick-film printing to form both the island and bridgestructures. In the example implementations described below, particularattention in printing the stretchable serpentine silver interconnects ispaid to the sinuous geometry (e.g., line width or angle), the observedperformance of the fabricated deice, and the interface of the printedserpentine bridges with the printed functional composite islands.

For example, integration of the elastic composite materials with adeterministic design approach of structural components provides anextremely versatile technique to produce stretchable electronics, e.g.,by embedding any type, or combination of conductive fillers into anelastic matrix to form an elastic, conductive composite. Employingelastic composite materials is an attractive approach for itsversatility, as electrical and elastic performance can be tailored basedon the ratio of composite materials. In addition, the unlimited numberof material choices, such as nanomaterials of various morphologicalshapes, are already seeing massive implementation in varioustechnologies and disciplines, and can be easily incorporated in thisprocess. The scope and limitations of the new printing strategy arediscussed and demonstrated below in the examples below. One exampleshows the practical utility of the disclosed technology illustrated in askin-worn, printed zinc battery with an area density capacity of 1.6mAh/cm⁻².

Example fabrication of “Island-Bridge” stretchable electronics device isas follows. As stretchable electronics continue to evolve from rigidtechnologies listed previously, it is imperative for the fabrication tobe versatile applied on to any substrates compatible withparticle-polymer composites. This becomes particularly challenging forepidermal and textile-based electronics that demand these devices to beinexpensive and scalable. These requirements, combined with the rise incomplex nanomaterial composites, will present unlimited possibilitiesfor inexpensive, high-performance and stretchable electronics.

FIG. 11A shows an illustrative diagram depicting an examplescreen-printing, fabrication method to produce a stretchable IBelectronics device using elastic carbon ink as functional islands andfollowed by elastic, silver bridges in a serpentine configuration (e.g.,line width greater than 150 microns). FIGS. 11B-11J show imagesdepicting features of an example stretchable IB device, duringfabrication. FIG. 11B shows the printed elastic carbon ink onwater-soluble tape. FIG. 11C shows an elastic, serpentine bridge printedon top of carbon. FIG. 11D shows a sample of the device after curing,which can be transferred to skin and have the water-soluble tape removedwith a simple washing step. FIG. 11E shows the printed sampletransferred on to skin. FIG. 11F shows the sample of FIG. 11E zoomed in.FIG. 11G shows the sample being compressed on the skin. FIG. 11H showsan example printed island-bridge directly produced on a textile. FIG.11I shows the sample of FIG. 11H zoomed in. FIG. 11J shows the samplebeing folded on the textile. FIG. 11K shows an illustration depicting anexample use of these stretchable IB electronics devices that can beexpanded for large-area electronics on skin and textiles.

As shown in FIG. 11A, a 3 by 3 array of functional islands connectedwith serpentine bridges were fabricated in two processes by examplescreen printing techniques. The fabrication method shown in FIG. 11Aincludes depositing inks, including example elastic composite inks, onto surfaces. For example, the method can include utilizing acomputer-aid design (CAD) software, such that any desired design can bepatterned into a custom designed, stainless steel stencil to controlwhere the ink is deposited onto a substrate. The method includes aprocess 1110 to print one or more elastic composite materials 100, e.g.,any engineered ink composite of any desired conductive filler andpolymers in accordance with the present technology, such as anelastic/graphitic ink, on a substrate using a stencil to form functionalislands. The method includes a process 1120 to print one or more elasticcomposite materials 100 to form bridge structures, e.g., in the form ofserpentine interconnects, to link the islands on the substrate, toproduce the stretchable IB electronics device 1100. For example, thewide variety of substrates are readily adaptable to printingtechnologies such as a water-soluble tape that can be used to aid in thedevice transfer onto the epidermis or directly on top of a textile.

The example shown in FIG. 11B of the printed elastic carbon ink on awater-soluble tape included, after subsequent curing of the firstprinted layer, mixing a highly conductive Ag-flake (e.g., 2-4 micron)with a resin of the elastic polymer in organic solvents to produce thedesired elastic composite ink. The elastic composite ink was printeddirectly on top in a specific serpentine, therefore acting as an elasticbridge between the functional islands, shown in FIG. 11C. Thoroughanalysis of each component's purpose in the ink was used foroptimization of the composite's elastic and conductive properties,discussed later in further detail.

After curing the printed inks on to a water-soluble tape, the tape canbe peeled from the carrier paper, flipped and attached onto skin that ispre-coated with a medical adhesive, as shown in FIG. 11D. For example,after applying considerable pressure to ensure adhesion, thewater-soluble tape was rinsed off gently with water in less than 30seconds. The example printed device remains on the skin with a highresolution without residue of substrate, and is capable of undergomultiple forms of deformation such as compression, pinching,indentations, as depicted in the images of FIGS. 11E, 11F and 11G. Byreversing the printing order, for example, the device can be printeddirectly on to the surface of a textiles, where both island and bridgescan undergo the same deformations, as depicted in the images of FIGS.11H, 11I and 11J. The diagram of FIG. 11K shows an example of a useremploying the printed stretchable IB electronics devices on body, e.g.,stretchable IB electronics device 1101 attachable directly on epidermisor stretchable IB electronics device 1102 attachable on textiles,robotic skins or other interactive, curvilinear surfaces, in which theused can be partially or completely covered with stretchableelectronics, e.g., due to the simplistic and versatility of thisfabrication large-area electronics, textiles.

The formulation of the elastic inks is important to achieve greatcontact with a rough surface of the skin. One example of the elasticcomposite material 100 includes the triblock copolymer SIS, in which theelastic composite material in the stretchable IB electronics device canachieve stretching with high elongation, e.g., greater than 1500%. Inexample implementations, the elastic conductive ink using SISdemonstrated very high stretchability while being able to bind asignificant amount of conductive filler such as silver flake or carbonmicron powder in the ink formulation. The unique elastic structure ofSIS includes both elastic blocks and plastic blocks which self-assembleinto a network of physical crosslinks which attributes to the highstretchability of the polymer. The serpentine bridges easily adhered tothe cervices and hills of skin even at the interface of theisland-bridge, even when stretched or twisted of the skin.

FIG. 12A shows a diagram showing geometric parameters for width, length,and angle of example serpentine bridges used in example embodiments ofthe stretchable IB electronics devices. The example serpentine bridgesare composed of unit cells, e.g., a “horseshoe” design, where its arcwidth (w) (e.g., >50 microns), arch radius (e.g., 10-45°), arc angle (θ)(e.g., 0-1000 microns), and linear arm (l) connecting unit cells can bevaried to determine the stretchable properties. For example, thesefeatures can be specifically designed using a computer-aided design(CAD) software to be cut into a stainless stencil for screen printing.

FIG. 12B shows an image of a stencil employed for printing electronicsof pre-cut design. FIG. 12C shows an image of stencil design forserpentine bridge with varied line width (e.g., w=150, 250, 500micron/um). For initial tests, the length of the linear arm was varied(e.g., 0, 500, and 1000 microns), as shown in the section of thestencil. These unit cells can create complex mechanical behaviors due totheir different dimensions and FEA modeling can be used to predict itsstretchability, and the addition of elastic polymer will additionaldegree of stretchability. A single straight line denoted as S and threeserpentine designs with the increasing linear arm length are identifiedin order as, 2, 3 are printed on PU and stretched from 0% to 100% overmultiple iterations. FIGS. 12D and 12E show optical images of printed,stretchable inks using varied serpentine design at 0% stretch (FIG. 12D)and 100% stretch (FIG. 12E). FIG. 12F shows a zoomed image providing acloser look at a single, extended serpentine turn, showing high qualityand resolution of the print that has no noticeable cracks even underdeformation. The adhesion to the PU is evident as well, with no signs ofdelaminating especially at the linear arms, which undergo most of thestrain.

FIGS. 12G and 12H show data plots depicting the change of resistance aseach printed design is stretched 100% (FIG. 12G) and tested for 10cycles of repetitive stretching (FIG. 12H). The measurement show theresistance of each device while being strained at a constant speed. Forexample, the three serpentine designs all demonstrated a superiorstability of their change of strength compared to the straight line whenbeing stretched 100%. Interestingly, the pattern of serpentines usingthe elastic composite ink provided different properties as compared toconventional serpentine designs using conventional materials, whichshowed that increasing the linear arc angle will typically result inbetter durability. For example, this distinction was attributed tonature or thick-film screen-printing where the deposited ink was boundtightly to the substrate. The tight binding is individually designed inthe ink formulation, so the delamination of printed composites from thesubstrate during flexing and stretching can be avoided. The solvent usedin the ink, e.g., toluene in this case, can partially react with thesubstrate and cause partial dissolution/swelling of the substratematerial, hence allow the ink composite to strongly bond to thesubstrate after the solvent is evaporated. However, as a tradeoff, whenthe IB structure is being stretched, the serpentine is unable to isolateitself from the substrate, hence being internally expanded along withthe substrate. The expansion of the composite can cause the resistanceof the serpentine to increase. While this can be partially overshadowedby the serpentine design, data from the example stretching tests showthe larger difference as linear arm length. Initially, as the linear armlength increases, the electrical conductivity becomes increasinglystable. However, above a certain length, the expansion of compositebecomes the dominant factor of the resistance of the serpentine due tothe extra linear arm length. Moreover, from a practical manufacturingangle, as the linear arm length increase, the occurrence of defectsincreases, as this location of the stencil is often more fragile, andthe complete pattern becomes harder to print. This anomaly can beattributed to the fine resolutions (e.g., less than 250 μm) of theseprints and that is tightly bonded to the substrate thus being stretchedlaterally as well. This may be attributed to why, for example, line 3with the 1000-micron length, had demonstrated relatively less durabilityas compared to the 500-micron length. Since the extended linear arm isperpendicular, the longer the length can exhibit stretching of its linewidth, which may cause deformation in the printed composite ink. Thisexample result is evident from the example cycling test shown in FIG.12H, where line 2 also demonstrated a superior durability compared tothe straight line and other serpentine designs.

FIGS. 13A-13I show images and data plots pertaining to evaluation ofexample island-bridge designs of example embodiments of stretchable IBelectronics devices. FIG. 13A shows an image of a sample mounted onto acustom-made, motorized stage. FIGS. 13B and 13C show images of aunstretched sample and stretched sample of 3 by 3 island-bridge arraywith designed imaging of island deformation, respectively. FIG. 13Dshows a data plot depicting the deformation of islands at differentisland-serpentine pairs stretched from 0% to 100%. FIGS. 13E and 13Fshow microscopic images of center island at 0% stretch (FIG. 13E) and100% stretch (FIG. 13F). FIG. 13G shows a data plot showing exampleconductivity measurements of biaxial stretching to 50% over 10 cycles.FIGS. 13H and 13I show microscopic images of corner island at 0% stretch(FIG. 13H) and 100% stretch (FIG. 13I).

The remarkable stretchability of the example serpentine designs usingthe example elastic composite materials and screen-printing technologieswere studied in conjunction with functional islands. For example, unlikedeterministic approaches that rely on serpentine bridges to accommodateall the strain, these example printed “island-bridge” can exhibit boththe serpentine and functional islands stretch when strained is applied.In an example evaluation using custom, mechanical stretching stage, forexample, an elastic composite ink composed of silver flake and SIS wasprinted in a serpentine design onto polyurethane as followed by anelastic ink formulation consisting of super-P and SIS, shown in FIG.13A. In the example design, there are different number of serpentinebridges connected to a specific bridge, such as the “side”, “center”,and “corner” designated in FIG. 13B. From a macro perspective, thecomplete device stretching is shown with uniformity, e.g., despite thedifference of serpentine connections that could add additional strain orthe risk of delamination, as illustrated in FIG. 13C.

When the functional islands were evaluated at a microscopic level,non-uniform expansion was noticeable, e.g., when compared to the“center” island. In FIG. 13C, the ratio of cross-sectional diametersshould have a consistent ratio of 1, for example, to maintain thecircular shape, but this was only demonstrated with the “center” island.This example demonstration by the center island included stretching from0% stretch (FIG. 13E) and at 100% stretch (FIG. 13F). The other “corner”and “side” islands exhibited higher strain along the lengths of theserpentine connections, reflecting the formation of an elliptical shapewhen strained from 0% (FIG. 13H) to 100% (FIG. 13I). Also, for theseexample implementations, pinholes were visible in the carbon ink at theinterfaces between the PU substrate, carbon island, and silverserpentine bridge when the ink is stretched. Since the “island”components require higher loadings of conductive carbon fillers tocompensate for their low conductive compared to the stretchable silver,serpentine, the carbon “island” is shifted more in proportional of thesilver ink. This may cause the example carbon island to form pinholes,delamination around the connection site, and disproportional deformationat different sits of the array. This presents an exciting aspect ascompared to lithographic structures.

In some example embodiments, the example stretchable electronics devicescan include intricate designs or arrangements of the array“island-bridge” array, e.g., using triangular, hexagon, and many moregeometrical structures between the stretchable island/bridgeconfiguration, which can present new types of behavior, e.g., especiallyevaluating the depth of the connection. These example different designsmay change the amount of surface area is available for functionalislands, e.g., as the IB array sacrifices active area to provide moredurability.

FIG. 14A-14E show images, illustrations and data for example embodimentsof a printed stretchable island-bridge zinc-silver oxide battery. FIG.14A shows an image of an example stencil design for a serpentine bridgethat can be employed in the example stretchable IB zinc-silver oxidebattery. FIG. 14B shows an illustrative diagram depicting an exampleepidermal energy storage device, e.g., a stretchable, rechargeable IBzinc-silver oxide battery 1420, conforming to skin in an interdigitateddesign of island-bridge. FIGS. 14C and 14D show images of an examplefinal print of the stretchable battery and its voltage output (FIG. 14C)and of the final printed stretchable battery surrounded around an indexfinger of a user. FIG. 14E shows a data plot depicting the charge anddischarge curves for the example rechargeable battery.

As shown in FIG. 14B, the stretchable, rechargeable IB zinc-silver oxidebattery 1420 includes a stretchable substrate 1422 including an elasticand electrically insulative material structured to conform to an outersurface of an object, e.g., such as skin, textile or other materialsurface of any object. The stretchable, rechargeable IB zinc-silveroxide battery 1420 includes a layer of a conductive material that formsthe island-bridge structure 1424, e.g., which can span in one or moredirections on the substrate 1422. In some examples of the battery 1420,the island-bridge structure 1424 includes silver. The stretchable,rechargeable IB zinc-silver oxide battery 1420 includes an underlayer ofa conductive material on a particular region over the island-bridgestructure 1424 to form a current collector structure 1426. In someexamples, the current collector structure includes carbon black (e.g.,SP). In some embodiments of the battery 1420, the current collectorstructure 1426 is patterned in an array over various portions of theisland-bridge structures 1424, which can include in the manner shown inthe example design depicted in FIG. 14B. The stretchable, rechargeableIB zinc-silver oxide battery 1420 includes an anode structure 1427formed over at least one of the current collector structure 1426. Thestretchable, rechargeable IB zinc-silver oxide battery 1420 includes acathode structure 1428 formed over at least another one of the currentcollector structure 1426. Various designs of the stretchable,rechargeable IB zinc-silver oxide battery 1420 can be produced such thatone or more anode structures 1427 are arranged to be separated andproximate one or more cathode structures 1428. In some embodiments ofthe stretchable, rechargeable IB zinc-silver oxide battery 1420, thearrangement of the anode structure 1427 and the cathode structure 1428can be built vertically, in which an electrolyte material is structuredbetween the anode and cathode.

The example design of the island-bridge structure shown in FIGS. 14A-14Dis quite adaptable to various technologies, e.g., especially forelectrochemical devices such as batteries, biofuel cells,supercapacitors, and chemical sensors that require two opposingelectronics. The results of the example implementations shown in FIGS.14-14E demonstrate the applicability of the printed “island-bridge” fora printed battery using the disclosed elastic composite materials. Theindividual engineered inks are synthesized for zinc and silver-oxideelectrodes using the example copolymer and powder composites of activematerial, conductive additives, and/or other metals to improve therechargeability of the desired product. For example, zinc chemistry wasselected for its safety and ability to print in the air, but essentiallyany battery chemistry can be applied to this format. The island-bridgearray was modified into an interdigitated design of zinc anode andsilver (II) oxide cathode, shown in FIG. 14A, e.g., demonstrating thereaction in shown in FIG. 14B. The example silver serpentine connectionswere printed first onto a polyurethane substrate, where they are allconnected by carbon islands. The zinc and cathode islands were thenprinted after that, a polyurethane pack was filled with a gelelectrolyte and finally sealed.

The example printed stretchable, rechargeable IB zinc-silver oxidebattery demonstrated good electrical and mechanical durability, as shownin FIGS. 14C and 14D, respectively, as the device can be easily wrappedaround an index finger. The charge and discharge curves of the firstcycle at 2 mA/cm are provided in FIG. 14E and followed by its cyclingstudy. For this example, the complete battery design covers an area of˜8 cm² which demonstrated a total capacity of 1.6 mAh, with an effectiveareal capacity of 2.42 mAh/cm² for the 4.15 mm² area for 16 pairs offunctional islands.

The example “island-bridge” designs for stretchable electronicsintegrate deterministic and intrinsic composite material designarchitectures through inexpensive, high-throughput screen-printingprocesses. The example stretchable devices were developed using thedisclosed elastic composite inks that can be tailored with anyconductive fillers and polymers specific to the application. The examplemechanical deformation studies evaluating the serpentine designs andradial deformation of islands show the complexity of the island-bridge.For example, composite inks of varied compositions and materials exhibitunique strain-stress profiles. These example results highlight thecomplexity of the collective conformability of the printed“island-bridge”. In some embodiments, the elastic conductive compositeinks can include high-aspect ratio fillers, such as silver nanowires andcarbon nanotubes. Other combinations of elastic polymer and conductiveutility materials can provide other durable and high-performanceepidermal electronics.

The low-cost and scalability of the example screen-printed stretchableelectronics devices introduces a cost-effective alternative with thesame ability to vary the design and components into a single, additiveprinting step. Furthermore, materials applicable to semiconductorprocessing are very limited, e.g., typically to one metal. The use ofink formulations allows any combination of conductive fillers andmaterials that vary in complexity across any technology. The developmentof a printed “island-bridge” may lead to a wide range of inexpensivestretchable electronics for a variety of applications. The serpentinedesigns are bound to the substrate but mechanical durability, which canbe improved by freeing the design from the substrate. The method ofsynthesizing and tailoring inks for large-scale printing of stretchabledevices holds great promise and study for conformal electronics.

Example embodiments of fabrication methods to produce the exampleelastic composite inks and example stretchable IB electronics devicesused in the example implementations are described.

Example chemicals and reagents used in the example implementationsinclude the following: Super-P Conductive Carbon Black (SP), toluene(Alfa Aesar), 200 proof Koptec (Decon Labs, King of Prussia, Pa.), Znpowder (Alfa Aesar), Ag₂O powder (Alfa Aesar), Bi₂O₃ (Alfa Aesar), anduniversal mold release provided from Smooth On. KOH, LiOH, polyacrylicacid, silver flake (<10 micron), and SIS (14% styrene) were obtainedfrom Sigma Aldrich, for example.

The example island-bridge stencil designs and devices were prepared asfollows. The fabrication of screen printing electronics in an“island-bridge” configuration used an MPM-SPM semi-automatic screenprinter (e.g., Speedline Technologies, Franklin, Mass.). The widevariety of serpentine and island designs were designed using CADsoftware, AutoCAD (e.g., Autodesk, San Rafael, Calif.). The design wasthen cut into a 300-micron thick, 12″ by 12″ stainless steel using alaser cutting (e.g., Metal Etch Services, San Marcos, Calif.). Due toimprove cleaning of the stencil from dried ink inside the stencilsfeatures, for example, the stencil was coated with mold release spray(e.g., SmoothOn, Inc., PA).

The example composite inks used in the example implementations wereformulated by dissolving 4 gram of SIS pellets in 10 mL with an analogvortex mixer (VMR) for 1 hour to make a viscous resin. The silver inkused for printing the example serpentine bridges was synthesized bymixing 1.2 grams of silver flake with 0.7 grams of the viscous resin.Additional 0.5 grams of 4 g of yttria stabilized zirconia grinding beads(e.g., 3 mm diameter, e.g., Inframat Advanced Materials) into the ink,then mixed using a dual asymmetric centrifugal mixer (e.g., FlacktekSpeedmixer, DAC 150.1 KV-K) at 1800 rpm for 30 min. The elastic carbonink was prepared by first dissolving 1.2 g of SIS pellets in 5 mL of 80%(v/v) toluene and 20% (v/v) ethanol with analog vortex mixer for 1 h.Then, 0.55 g of composite Super-P were mixed into the SIS solution inthe dual asymmetric centrifugal mixer at 3000 rpm for 5 min. Due to thehigh shear shores generating heat from the mixing, for example, the inkis let to cool before adding 2 g of the yttria-stabilized zirconiagrinding beads and additional 4 mL of the toluene/ethanol solution wereadded and underwent further mixing of 3000 rpm for 30 min. The batteryinks and electrolytes were employed as previously described for theprinted, stretchable battery. The example stretchable devices used a26-micron thick polyurethane sheet (e.g., Delstar Technologies Inc.Middletown, Del.). The transfer any printed device to the epidermis useda water-soluble wave solder tape 5415 (e.g., 3M, St. Paul, Minn.) as thecarrier. Printing directly on to a textile, the fabric was apolyurethane laminated (PUL) textile (e.g., Diaper Sewing Supplies,Fenton, Mo.).

The example stretching tests were conducted on a custom linear orbiaxial stretching stage of a motorized linear stage and controller(e.g., A-LST0250A-E01 Stepper Motor and Controller, Zaber Technologies,Vancouver, Canada). The samples were programmed to constantly stretch ata speed of 0.08 mm s⁻¹ from 0% to 100% and back to 0% as one cycle. Theresistance was measured at 22 pt s⁻¹ using a digital multimeter (e.g.,Agilent, Santa Clara, Calif.) during the ten cycles. The speed andlength of the physical strain were programmed into a scripting software(e.g., Zaber console, Zaber Technologies, Vancouver, Canada).

The electrochemical tests were conducted at room temperature, forexample. The electrochemical cycling tests were conducted with Arbinelectrochemical cycler channels. Electrochemical cycling tests wereconducted with 1 mA cm⁻² discharge current and charge current for thesubsequent cycles. The discharge cut-off voltage was 0.8 V and thecharge cut-off voltage was 2.3 V.

Example Applications

In some example embodiments in accordance with the present technology,the disclosed elastic composite materials can be used to produceconformal supercapacitor devices that includes the copolymer 101 andutility material 102 including a conductive material with high surfacearea (e.g. carbon, carbon nanotubes, graphene, etc.) that can storeenergy in an electric field.

In some example embodiments in accordance with the present technology,the disclosed elastic composite materials can be used to produceconformal energy harvester devices that includes the copolymer 101 andutility material 102 including piezoelectric and/or triboelectricfillers that can convert mechanical energy into electric energy. Forexample, a printed, stretchable triboelectric device can be used as anultra-thin, flexible transducer for actuating signals or sensing noise,e.g., by having the example stretchable triboelectric device between toelectrical contacts.

Also, for example, a conformal energy harvester device can include thecopolymer 101 and utility material 102 including photovoltaic polymer orsemiconductor, such that the device can convert light into electricalenergy or vice versa to formulate a light emitting display.

In some example embodiments in accordance with the present technology,the disclosed elastic composite materials can be used to producestretchable transistor devices that includes the copolymer 101 andutility material 102 including semiconductor material doped withimpurities to synthesize a gate, gate dielectric, source, drain to formthe transistor.

In some example embodiments in accordance with the present technology,the disclosed elastic composite materials can be used to produce aconformal color coat (e.g., paint) that includes the copolymer 101 andutility material 102 such as a colorant dye.

In some example embodiments in accordance with the present technology,the disclosed elastic composite materials can include a stretchableslurry for a silicon lithium ion battery (SLIB) anode, which includesthe copolymer 101 and utility material 102 including siliconmicro/nanoparticles, carbon additive, and a solvent. In some examples,the stretchable slurry can include 0.1%-20% wt of SIS, 80%-99.9% wt ofan electrically conductive filler, and 10% wt additive material toformulate the slurry that is casted onto a conductive surface (e.g.,copper foil), which can be set into a coin cell.

For example, the stretchable polymer forms an elastic network that canprevent pulverization, where the expansion of silicon upon lithiationcan cause the fracture of an anode. Moreover, the example SLIB-typeelastic composite material can improve the battery manufacturing orprocessing. For example, the use of the SLIB-type elastic compositematerial does not require water, unlike conventional anodes, in whichwater is a difficult solvent to disperse silicon, thereby simplifyingslurry synthesis.

FIG. 15 shows a diagram of an example stretchable wearable sensor 1500in accordance with the present technology. The example stretchablesensor 1500 is shown in FIG. 15 as configured as a 3-electrodeelectrochemical sensor, and it is understood the example stretchablesensor 1500 can include fewer or greater electrodes, and can beconfigured for other sensor applications, such as electrophysiologicalsensing or other. The sensor 1500 includes a stretchable substrate 1501,e.g., including an elastic and electrically insulative materialstructured to conform to an outer surface of an object, such as skin.The sensor 1500 includes one or more electrodes, e.g., a workingelectrode 1504, counter electrode 1502 and reference electrode 1506,arranged over the stretchable substrate 1501. The one or more electrodes1504, 1502 and/or 1506 include an example elastic composite materialincluding an electrical conductor as the utility material 102, and thecopolymer 101, e.g., SIS, configured to form a hyperelastic binder thatcreates contacts between particles of the electrical conductor within anetwork formed by the copolymer. In some examples for an electrochemicalsensor, the working electrode 1504 and/or the counter electrode 1502 caninclude a functionalized coating with a catalytic layer for mediating anelectrochemical reaction detectable by the stretchable sensor 1500.

FIG. 16 shows a diagram of an example stretchable battery 1600configured as a stretchable battery layer 1601 attached to an adhesive1603, which attaches to skin of a user or other surface of an object,and electrically coupled to a support base 1605 of a sensor device,e.g., such as an electronics unit and/or sensor unit. The stretchablebattery 1601 can include any of the example embodiments of thestretchable battery in accordance with the present technology. In theexample shown in FIG. 16, the stretchable battery layer 1601 can beintegrated into the adhesive layer 1603 to form an adhesive patch, whichcan be applied to any surface, e.g., skin. The device base 1605 caninclude supportive electronics units, such as communication and powermanagement, sensor electronics, etc., which can be a mounted dongle thatattaches to the adhesive patch. The example stretchable device designwould extremely reduce the bulk associated with conventional wearablesensors, and make the wearable device more compliant and therefore morecomfortable to a user.

The examples above include various stretchable electronics devicesand/or stretchable materials that can be made with the elastic compositematerial 100 that results in these different applications and use cases.

EXAMPLES

The following examples are illustrative of several embodiments inaccordance with the present technology. Other exemplary embodiments ofthe present technology may be presented prior to the following listedexamples, or after the following listed examples.

In some embodiments in accordance with the present technology (example1), an elastic composite material includes a first material having aparticular electrical, mechanical or optical property; and a multi-blockcopolymer configured to form a hyperelastic binder that creates contactbetween the first material and the multi-block copolymer, in which theelastic composite material is structured to stretch at least 500% in atleast one direction of the material and to exhibit the particularelectrical, mechanical or optical property imparted from the firstmaterial.

Example 2 includes the elastic composite material of example 1, in whichthe % wt of the first material is at least 60% and the % wt of the blockcopolymer is at most 40%.

Example 3 includes the elastic composite material of example 1, in whichthe % wt of the first material is at least 80% and the % wt of the blockcopolymer is at most 20%.

Example 4 includes the elastic composite material of example 1, in whichthe elastic composite material is structured to stretch at least 1000%in the at least one direction.

Example 5 includes the elastic composite material of example 1, in whichthe elastic composite material is structured to stretch at least 500% inat least two directions.

Example 6 includes the elastic composite material of example 5, in whichthe at least two directions are perpendicular.

Example 7 includes the elastic composite material of example 1, in whichthe multi-block copolymer includes polystyrene-polyisoprene-polystyrene(SIS).

Example 8 includes the elastic composite material of example 1, in whichthe multi-block copolymer includes a thermoplastic elastomer includingstyrene-ethylene/butylene-styrene (SEBS) block copolymer,styrene-ethylene/propylene-styrene (SEPS), or styrene-butadiene-styrene(SBS) block copolymer.

Example 9 includes the elastic composite material of example 1, in whichthe first material includes an electrical conductor, an electricalinsulator, a dielectric, a ceramic, or a semiconductor.

Example 10 includes the elastic composite material of example 1, furtherincluding one or more additive materials.

Example 11 includes the elastic composite material of example 10, inwhich the % wt of the first material is at least 75%, the % wt of theblock copolymer is at most 20%, and the % wt of the one or more additivematerials is between 0.1% and 10%.

Example 12 includes the elastic composite material of example 10, inwhich the one or more additive materials includes a metal, asemiconductor, an organic polymer, an inorganic polymer, a ceramic, or acomposite material.

Example 13 includes the elastic composite material of example 10, inwhich the one or more additive materials includes a nanoparticle, ananowire, a nanofiber, or a nanoflake.

Example 14 includes the elastic composite material of example 10, inwhich the one or more additive materials includes a mineral oil, and the% wt of the mineral oil is between 1% and 2% of the elastic compositematerial.

Example 15 includes the elastic composite material of example 10, inwhich the one or more additive materials includes zinc oxide and bismuthoxide, and the % wt of the zinc oxide and bismuth oxide is each between5% and 10%.

Example 16 includes the elastic composite material of example 10, inwhich the one or more additive materials includes a color agent.

Example 17 includes the elastic composite material of example 1, inwhich the multi-block copolymer forms a hyperelastic binder that createscontacts between particles of the first material within a network formedby the multi-block copolymer.

Example 18 includes the elastic composite material of example 1, inwhich the elastic composite material does not include a cross-linker forcross-linking strands of a polymer in the elastic composite material.

Example 19 includes the elastic composite material of example 1, inwhich the elastic composite material is in the form of a printable ink.

In some embodiments in accordance with the present technology (example20), a method for producing a stretchable electronics device includesproviding an electrically conductive ink that includes an elasticcomposite material including an electrically conductive material and amulti-block copolymer configured to form a hyperelastic binder thatcreates contact between the electrically conductive material and themulti-block copolymer; producing a first structure on a stretchablesubstrate by printing the electrically conductive ink through a firstportion of a stencil structured to have a first design to form thegeometry of the first structure, in which the stretchable substrateincludes an elastic material structured to conform to an outer surfaceof an object; and producing a second structure on the stretchablesubstrate to produce a stretchable electronics article by printing theelectrically conductive ink through the first portion of the stencil, ora second portion of the stencil structured to have a second design, orboth the first portion and the second portion, to form the geometry ofthe second structure, in which the stretchable electronics article isable to stretch at least 500% in at least one direction and to exhibitelectrical conductivity in the first structure while being stretched.

Example 21 includes the method of example 20, in which the stretchablesubstrate includes an electrically insulative material.

Example 22 includes the method of example 20, in which the multi-blockcopolymer of the elastic composite material includes polystyrene-polyisoprene-polystyrene (SIS).

Example 23 includes the method of example 20, in which the multi-blockcopolymer includes a thermoplastic elastomer includingstyrene-ethylene/butylene-styrene (SEBS) block copolymer,styrene-ethylene/propylene-styrene (SEPS), or styrene-butadiene-styrene(SBS) block copolymer.

Example 24 includes the method of example 20, in which the providing theelectrically conductive ink includes providing a (i) first electricallyconductive ink including a first elastic composite material including afirst electrically conductive material and the multi-block copolymer,and (ii) a second electrically conductive ink including a second elasticcomposite material including a second electrically conductive materialand the multi-block copolymer, the second electrically conductivematerial different than the first electrically conductive material, inwhich the producing the first structure includes printing the firstelectrically conductive ink, and in which the producing the secondstructure includes printing the second electrically conductive material.

Example 25 includes the method of example 24, in which the firststructure forms a conductive underlayer of the stretchable electronicsarticle, and the second structure forms an active layer that is printedover the conductive underlayer of the stretchable electronics device.

Example 26 includes the method of example 25, further includingproducing a third structure on the conductive underlayer to produce thestretchable electronics article by printing a third electricallyconductive ink, which includes a third elastic composite material,through a third portion of the stencil structured to have a third designto form the geometry of the third structure, in which the third elasticcomposite material includes a third electrically conductive materialdifferent than the first and the second electrically conductivematerials, and the multi-block copolymer.

Example 27 includes the method of example 26, in which the stretchableelectronics article is a rechargeable Zn—Ag₂O battery, in which thefirst electrically conductive material includes carbon black, the secondelectrically conductive material includes zinc, and the thirdelectrically conductive material includes silver oxide.

Example 28 includes the method of example 20, in which the stretchablesubstrate includes a textile.

Example 29 includes the method of example 28, in which the stretchablesubstrate includes a thermoplastic polyurethane sheet on the textile.

Example 30 includes the method of example 20, further including curingthe printed electrically conductive ink on the stretchable substrate.

Example 31 includes the method of example 20, further includingproducing one or more outer features on the stretchable electronicsarticle to electrically connect at least some of the structures or toprovide contact structures that electrically connect to at least some ofthe structures.

Example 32 includes the method of example 20, further including forminga protective sheet over at least a portion of the produced stretchableelectronics article.

Example 33 includes the method of example 20, in which the multi-blockcopolymer forms a hyperelastic binder that creates contacts betweenparticles of the electrically conductive material within a networkformed by the multi-block copolymer, and in which the providedelectrically conductive ink does not include a cross-linker forcross-linking a polymer in the electrically conductive ink.

In some embodiments in accordance with the present technology (example34), a stretchable electronics device includes a stretchable substrateincluding an elastic and electrically insulative material structured toconform to an outer surface of an object; and an electrode arranged overthe stretchable substrate, in which the electrode is formed from anelastic composite material including an electrical conductor, and amulti-block copolymer configured to form a hyperelastic binder thatcreates contacts between particles of the electrical conductor within anetwork formed by the multi-block copolymer.

Example 35 includes the stretchable electronics device of example 34, inwhich the electrode is structured to stretch at least 500% in at leastone direction and to exhibit electrical conductivity in the electrode.

Example 36 includes the stretchable electronics device of example 34, inwhich the electrode is structured to stretch at least 1000% in the atleast one direction and to exhibit electrical conductivity in theelectrode.

Example 37 includes the stretchable electronics device of example 34, inwhich the electrode is structured to stretch at least 500% in at leasttwo directions, and the at least two directions are perpendicular.

Example 38 includes the stretchable electronics device of example 34, inwhich the multi-block copolymer of the elastic composite materialincludes polystyrene-polyisoprene-polystyrene (SIS).

Example 39 includes the stretchable electronics device of example 34, inwhich the % wt of the first material is at least 60% and the % wt of theblock copolymer is at most 40%, or in which the % wt of the firstmaterial is at least 80% and the % wt of the block copolymer is at most20%.

Example 40 includes the stretchable electronics device of example 34,further including a second electrode spaced from the first electrode, inwhich the second electrode is formed from a second elastic compositematerial including a second electrical conductor and the multi-blockcopolymer configured to form a hyperelastic binder that creates contactsbetween particles of the second electrical conductor within a networkformed by the multi-block copolymer.

Example 41 includes the stretchable electronics device of example 40, inwhich the device includes a power storage device having an anode and acathode corresponding to the electrode and the second electrode,respectively.

Example 42 includes the stretchable electronics device of example 41, inwhich the electrical conductor of the anode includes zinc and the secondelectrical conductor of the cathode includes silver oxide.

Example 43 includes the stretchable electronics device of example 40,further including a conductive layer attached to the stretchablesubstrate and configured under the first electrode, the secondelectrode, or both the first and second electrodes, in which theconductor layer is formed from a third elastic composite materialincluding a third electrical conductor and the multi-block copolymerconfigured to form a hyperelastic binder that creates contacts betweenparticles of the third electrical conductor within a network formed bythe multi-block copolymer.

Example 44 includes the stretchable electronics device of example 43, inwhich the conductive layer includes carbon black.

Example 45 includes the stretchable electronics device of example 43, inwhich the device includes a power storage device having an anode and acathode corresponding to the electrode and the second electrode,respectively, and the conductive layer is a current collector of thepower storage device, in which the anode and the cathode are stackedvertically over the stretchable substrate with an electrolyte materialin between the anode and the cathode.

Example 46 includes the stretchable electronics device of example 34,further including a second electrode spaced from the first electrode, inwhich the second electrode is formed from the elastic compositematerial.

Example 47 includes the stretchable electronics device of example 46, inwhich the device includes a sensor.

Example 48 includes the stretchable electronics device of example 34,further including an electrical contact on the stretchable substrate andelectrically coupled to the electrode.

Example 49 includes the stretchable electronics device of example 34,further including a protective sheet over at least a portion of thestretchable electronics device.

Example 50 includes the stretchable electronics device of example 49, inwhich the protective sheet includes polyurethane.

In some embodiments in accordance with the present technology (example51), a stretchable battery includes a stretchable substrate including anelastic and electrically insulative material structured to conform to anouter surface of an object; a current conductor layer attached to thestretchable substrate, in which the current conductor layer includes afirst elastic composite material including a first electrical conductorand a multi-block copolymer configured to form a first hyperelasticbinder that creates contacts between particles of the first electricalconductor within a network formed by the multi-block copolymer; an anodeattached to the current conductor layer and arranged over thestretchable substrate, in which the anode includes a second elasticcomposite material including a second electrical conductor and themulti-block copolymer configured to form a second hyperelastic binderthat creates contacts between particles of the second electricalconductor within a network formed by the multi-block copolymer; and acathode arranged over the stretchable substrate, in which the cathodeincludes a third elastic composite material including a third electricalconductor and the multi-block copolymer configured to form a thirdhyperelastic binder that creates contacts between particles of the thirdelectrical conductor within a network formed by the multi-blockcopolymer, in which the stretchable battery is operable to store energywhile undergoing stretching.

Example 52 includes the stretchable battery of example 51, in which thecurrent conductor layer, the anode and the cathode are structured tostretch at least 500% in at least one direction and concurrently exhibitelectrical conductivity.

Example 53 includes the stretchable battery of example 51, in which thecurrent conductor layer, the anode and the cathode are structured tostretch at least 1000% in at least one direction and concurrentlyexhibit electrical conductivity.

Example 54 includes the stretchable battery of example 51, in which thecurrent conductor layer, the anode and the cathode are structured tostretch at least 500% in at least two directions and concurrentlyexhibit electrical conductivity, and the at least two directions areperpendicular.

Example 55 includes the stretchable battery of example 51, in which themulti-block copolymer of the elastic composite material includespolystyrene-polyisoprene-polystyrene (SIS).

Example 56 includes the stretchable battery of example 51, in which thefirst electrical conductor of the current collector layer includescarbon black, the second electrical conductor of the anode includeszinc, and the third electrical conductor of the cathode includes silveroxide.

Example 57 includes the stretchable battery of example 51, in which the% wt of at least one of the first, second or third electrical conductorsis at least 60% and the % wt of the block copolymer is at most 40%.

Example 58 includes the stretchable battery of example 51, in which theanode and the cathode are stacked vertically over the stretchablesubstrate, the stretchable battery further including an electrolytematerial arranged in between the anode and the cathode; and a secondcurrent collector layer attached to the cathode on a side opposite theelectrolyte.

Example 59 includes the stretchable battery of example 58, furtherincluding a first electrical contact electrically coupled to the currentcollector layer and a second electrical contact electrically coupled tothe second current collector layer.

Example 60 includes the stretchable battery of example 51, furtherincluding a protective sheet over at least a portion of the stretchablebattery.

Example 61 includes the stretchable battery of example 60, in which theprotective sheet includes polyurethane.

Example 62 includes the stretchable battery of example 51, in which theanode and the cathode are spaced horizontally over the stretchablesubstrate, the stretchable battery further including an electrolytematerial arranged in between the anode and the cathode, in which thecurrent collector layer includes two separate portions including a firstportion attached to the anode and a second portion attached to thecathode on a side opposite the electrolyte.

Example 63 includes the stretchable battery of example 62, furtherincluding a first electrical contact electrically coupled to the currentcollector layer and a second electrical contact electrically coupled tothe second current collector layer.

In some embodiments in accordance with the present technology (example64), a stretchable battery including a stretchable substrate includingan elastic and electrically insulative material structured to conform toan outer surface of an object; a first electrical interconnectionstructure and a second electrical interconnection structure eachattached to the stretchable substrate and having a periodic curvedhorseshoe geometry configured to connect unit cell regions positioned onthe electrical interconnection structure, in which the first and thesecond interconnection structures include a first elastic compositematerial including a first electrical conductor and a multi-blockcopolymer configured to form a first hyperelastic binder that createscontacts between particles of the first electrical conductor within anetwork formed by the multi-block copolymer; a plurality of currentconductor components attached to the electrical interconnectionstructure at the unit cell regions, in which the current conductor layerincludes a second elastic composite material including a secondelectrical conductor and a multi-block copolymer configured to form asecond hyperelastic binder that creates contacts between particles ofthe second electrical conductor within a network formed by themulti-block copolymer; a plurality of anodes attached to the currentconductor component over the unit cell regions of the first electricalinterconnection structure, in which the anodes include a third elasticcomposite material including a third electrical conductor and themulti-block copolymer configured to form a third hyperelastic binderthat creates contacts between particles of the third electricalconductor within a network formed by the multi-block copolymer; and aplurality of cathodes attached to the current conductor component overthe unit cell regions of the second electrical interconnectionstructure, in which the cathodes include a fourth elastic compositematerial including a fourth electrical conductor and the multi-blockcopolymer configured to form a fourth hyperelastic binder that createscontacts between particles of the fourth electrical conductor within anetwork formed by the multi-block copolymer, in which the stretchablebattery is operable to store energy while undergoing stretching.

Example 65 includes the stretchable battery of example 64, in which thefirst and second electrical interconnection structures, the currentconductor component, the anode and the cathode are structured to stretchat least 500% in at least one direction and concurrently exhibitelectrical conductivity.

Example 66 includes the stretchable battery of example 64, in which thefirst and second electrical interconnection structures, the currentconductor component, the anode and the cathode are structured to stretchat least 1000% in at least one direction and concurrently exhibitelectrical conductivity.

Example 67 includes the stretchable battery of example 64, in which thefirst and second electrical interconnection structures, the currentconductor component, the anode and the cathode are structured to stretchat least 500% in at least two directions and concurrently exhibitelectrical conductivity, and the at least two directions areperpendicular.

Example 68 includes the stretchable battery of example 64, in which themulti-block copolymer of the elastic composite material includespolystyrene-polyisoprene-polystyrene (SIS).

Example 69 includes the stretchable battery of example 64, in which thefirst electrical conductor of the electrical interconnection structureincludes silver, the second electrical conductor of the currentcollector component includes carbon black, the third electricalconductor of the anode includes zinc, and the fourth electricalconductor of the cathode includes silver oxide.

Example 70 includes the stretchable battery of example 64, in which theunit cell regions have an area of 5 mm² or less.

Example 71 includes the stretchable battery of example 64, in which thefirst and second electrical interconnection structures each include fourbranches including each having four of the unit cell regions such thatthe stretchable battery includes 16 anode-cathode pairs, in which thestretchable battery includes a total footprint of 8 cm² or less.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any invention or of what may beclaimed, but rather as descriptions of features that may be specific toparticular embodiments of particular inventions. Certain features thatare described in this patent document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments.

Only a few implementations and examples are described and otherimplementations, enhancements and variations can be made based on whatis described and illustrated in this patent document.

What is claimed is:
 1. A stretchable battery, comprising: a stretchablesubstrate including an elastic and electrically insulative materialstructured to conform to an outer surface of an object; a currentconductor layer attached to the stretchable substrate, wherein thecurrent conductor layer includes a first elastic composite materialcomprising a first electrical conductor and a multi-block copolymerconfigured to form a first hyperelastic binder that creates contactsbetween particles of the first electrical conductor within a networkformed by the multi-block copolymer; an anode attached to the currentconductor layer and arranged over the stretchable substrate, wherein theanode includes a second elastic composite material comprising a secondelectrical conductor and the multi-block copolymer configured to form asecond hyperelastic binder that creates contacts between particles ofthe second electrical conductor within a network formed by themulti-block copolymer; and a cathode arranged over the stretchablesubstrate, wherein the cathode includes a third elastic compositematerial comprising a third electrical conductor and the multi-blockcopolymer configured to form a third hyperelastic binder that createscontacts between particles of the third electrical conductor within anetwork formed by the multi-block copolymer, wherein the stretchablebattery is operable to store energy while undergoing stretching.
 2. Thestretchable battery of claim 1, wherein the current conductor layer, theanode and the cathode are structured to stretch at least 500% in atleast one direction and concurrently exhibit electrical conductivity. 3.The stretchable battery of claim 1, wherein the current conductor layer,the anode and the cathode are structured to stretch at least 1000% in atleast one direction and concurrently exhibit electrical conductivity. 4.The stretchable battery of claim 1, wherein the current conductor layer,the anode and the cathode are structured to stretch at least 500% in atleast two directions and concurrently exhibit electrical conductivity,and the at least two directions are perpendicular.
 5. The stretchablebattery of claim 1, wherein the multi-block copolymer of the elasticcomposite material includes polystyrene-polyisoprene-polystyrene (SIS).6. The stretchable battery of claim 1, wherein the first electricalconductor of the current collector layer includes carbon black, thesecond electrical conductor of the anode includes zinc, and the thirdelectrical conductor of the cathode includes silver oxide.
 7. Thestretchable battery of claim 1, wherein the % wt of at least one of thefirst, second or third electrical conductors is at least 60% and the %wt of the block copolymer is at most 40%.
 8. The stretchable battery ofclaim 1, wherein the anode and the cathode are stacked vertically overthe stretchable substrate, the stretchable battery further comprising:an electrolyte material arranged in between the anode and the cathode;and a second current collector layer attached to the cathode on a sideopposite the electrolyte.
 9. The stretchable battery of claim 8, furthercomprising: a first electrical contact electrically coupled to thecurrent collector layer and a second electrical contact electricallycoupled to the second current collector layer.
 10. The stretchablebattery of claim 1, further comprising: a protective sheet over at leasta portion of the stretchable battery.
 11. The stretchable battery ofclaim 1, wherein the anode and the cathode are spaced horizontally overthe stretchable substrate, the stretchable battery further comprising:an electrolyte material arranged in between the anode and the cathode,wherein the current collector layer includes two separate portionsincluding a first portion attached to the anode and a second portionattached to the cathode on a side opposite the electrolyte.
 12. Thestretchable battery of claim 12, further comprising: a first electricalcontact electrically coupled to the current collector layer and a secondelectrical contact electrically coupled to the second current collectorlayer.
 13. A stretchable battery, comprising: a stretchable substrateincluding an elastic and electrically insulative material structured toconform to an outer surface of an object; a first electricalinterconnection structure and a second electrical interconnectionstructure each attached to the stretchable substrate and having aperiodic curved horseshoe geometry configured to connect unit cellregions positioned on the electrical interconnection structure, whereinthe first and the second interconnection structures include a firstelastic composite material comprising a first electrical conductor and amulti-block copolymer configured to form a first hyperelastic binderthat creates contacts between particles of the first electricalconductor within a network formed by the multi-block copolymer; aplurality of current conductor components attached to the electricalinterconnection structure at the unit cell regions, wherein the currentconductor layer includes a second elastic composite material comprisinga second electrical conductor and a multi-block copolymer configured toform a second hyperelastic binder that creates contacts betweenparticles of the second electrical conductor within a network formed bythe multi-block copolymer; a plurality of anodes attached to the currentconductor component over the unit cell regions of the first electricalinterconnection structure, wherein the anodes include a third elasticcomposite material comprising a third electrical conductor and themulti-block copolymer configured to form a third hyperelastic binderthat creates contacts between particles of the third electricalconductor within a network formed by the multi-block copolymer; and aplurality of cathodes attached to the current conductor component overthe unit cell regions of the second electrical interconnectionstructure, wherein the cathodes include a fourth elastic compositematerial comprising a fourth electrical conductor and the multi-blockcopolymer configured to form a fourth hyperelastic binder that createscontacts between particles of the fourth electrical conductor within anetwork formed by the multi-block copolymer, wherein the stretchablebattery is operable to store energy while undergoing stretching.
 14. Thestretchable battery of claim 13, wherein the first and second electricalinterconnection structures, the current conductor component, the anodeand the cathode are structured to stretch at least 500% in at least onedirection and concurrently exhibit electrical conductivity.
 15. Thestretchable battery of claim 13, wherein the first and second electricalinterconnection structures, the current conductor component, the anodeand the cathode are structured to stretch at least 1000% in at least onedirection and concurrently exhibit electrical conductivity.
 16. Thestretchable battery of claim 13, wherein the first and second electricalinterconnection structures, the current conductor component, the anodeand the cathode are structured to stretch at least 500% in at least twodirections and concurrently exhibit electrical conductivity, and the atleast two directions are perpendicular.
 17. The stretchable battery ofclaim 13, wherein the multi-block copolymer of the elastic compositematerial includes polystyrene-polyisoprene-polystyrene (SIS).
 18. Thestretchable battery of claim 13, wherein the first electrical conductorof the electrical interconnection structure includes silver, the secondelectrical conductor of the current collector component includes carbonblack, the third electrical conductor of the anode includes zinc, andthe fourth electrical conductor of the cathode includes silver oxide.19. The stretchable battery of claim 13, wherein the first and secondelectrical interconnection structures each include a plurality ofbranches including each having a plurality of the unit cell regions. 20.A method for producing a stretchable electronics device, comprising:providing an electrically conductive ink that includes an elasticcomposite material comprising an electrically conductive material and amulti-block copolymer configured to form a hyperelastic binder thatcreates contact between the electrically conductive material and themulti-block copolymer; producing a first structure on a stretchablesubstrate by printing the electrically conductive ink through a firstportion of a stencil structured to have a first design to form thegeometry of the first structure, wherein the stretchable substrateincludes an elastic and electrically insulative material structured toconform to an outer surface of an object; and producing a secondstructure on the stretchable substrate to produce a stretchableelectronics article by printing the electrically conductive ink throughthe first portion of the stencil, or a second portion of the stencilstructured to have a second design, or both the first portion and thesecond portion, to form the geometry of the second structure, whereinthe stretchable electronics article is able to stretch at least 500% inat least one direction and to exhibit electrical conductivity in thefirst structure while being stretched.
 21. The method of claim 20,wherein the multi-block copolymer of the elastic composite materialincludes polystyrene-polyisoprene-polystyrene (SIS).
 22. The method ofclaim 20, wherein the multi-block copolymer includes a thermoplasticelastomer including styrene-ethylene/butylene-styrene (SEBS) blockcopolymer, styrene-ethylene/propylene-styrene (SEPS), orstyrene-butadiene-styrene (SBS) block copolymer.
 23. The method of claim20, wherein the providing the electrically conductive ink includesproviding a (i) first electrically conductive ink comprising a firstelastic composite material including a first electrically conductivematerial and the multi-block copolymer, and (ii) a second electricallyconductive ink comprising a second elastic composite material includinga second electrically conductive material and the multi-block copolymer,the second electrically conductive material different than the firstelectrically conductive material, wherein the producing the firststructure includes printing the first electrically conductive ink, andwherein the producing the second structure includes printing the secondelectrically conductive material.
 24. The method of claim 23, whereinthe first structure forms a conductive underlayer of the stretchableelectronics article, and the second structure forms an active layer thatis printed over the conductive underlayer of the stretchable electronicsdevice.
 25. The method of claim 24, further comprising: producing athird structure on the conductive underlayer to produce the stretchableelectronics article by printing a third electrically conductive ink,which comprises a third elastic composite material, through a thirdportion of the stencil structured to have a third design to form thegeometry of the third structure, wherein the third elastic compositematerial includes a third electrically conductive material differentthan the first and the second electrically conductive materials, and themulti-block copolymer.
 26. The method of claim 25, wherein thestretchable electronics article is a rechargeable Zn—Ag₂O battery,wherein the first electrically conductive material includes carbonblack, the second electrically conductive material includes zinc, andthe third electrically conductive material includes silver oxide. 27.The method of claim 20, wherein the stretchable substrate includes atextile.
 28. The method of claim 20, further comprising: producing oneor more outer features on the stretchable electronics article toelectrically connect at least some of the structures or to providecontact structures that electrically connect to at least some of thestructures.
 29. The method of claim 20, further comprising: forming aprotective sheet over at least a portion of the produced stretchableelectronics article.
 30. The method of claim 20, wherein the multi-blockcopolymer forms a hyperelastic binder that creates contacts betweenparticles of the electrically conductive material within a networkformed by the multi-block copolymer, and wherein the providedelectrically conductive ink does not include a cross-linker forcross-linking a polymer in the electrically conductive ink.